/* -*- mode: C -*-  */
/*
   IGraph library.
   Copyright (C) 2006-2012  Gabor Csardi <csardi.gabor@gmail.com>
   334 Harvard street, Cambridge, MA 02139 USA

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301 USA

*/

#include "igraph_topology.h"
#include "igraph_memory.h"
#include "igraph_adjlist.h"
#include "igraph_interface.h"
#include "igraph_interrupt_internal.h"
#include "igraph_constructors.h"
#include "igraph_conversion.h"
#include "igraph_stack.h"
#include "igraph_attributes.h"
#include "igraph_structural.h"
#include "igraph_isoclasses.h"
#include "config.h"

const unsigned int igraph_i_isoclass_3[] = {  0, 1, 1, 3, 1, 5, 6, 7,
                                              1, 6, 10, 11, 3, 7, 11, 15,
                                              1, 6, 5, 7, 10, 21, 21, 23,
                                              6, 25, 21, 27, 11, 27, 30, 31,
                                              1, 10, 6, 11, 6, 21, 25, 27,
                                              5, 21, 21, 30, 7, 23, 27, 31,
                                              3, 11, 7, 15, 11, 30, 27, 31,
                                              7, 27, 23, 31, 15, 31, 31, 63
                                           };

const unsigned int igraph_i_isoclass_3_idx[] = { 0, 4, 16, 1, 0, 32, 2, 8, 0 };

const unsigned int igraph_i_isoclass_4[] = {
    0,   1,   1,   3,   1,   3,   3,   7,   1,   9,  10,  11,  10,
    11,  14,  15,   1,  10,  18,  19,  20,  21,  22,  23,   3,  11,
    19,  27,  21,  29,  30,  31,   1,  10,  20,  21,  18,  19,  22,
    23,   3,  11,  21,  29,  19,  27,  30,  31,   3,  14,  22,  30,
    22,  30,  54,  55,   7,  15,  23,  31,  23,  31,  55,  63,   1,
    10,   9,  11,  10,  14,  11,  15,  18,  73,  73,  75,  76,  77,
    77,  79,  10,  81,  73,  83,  84,  85,  86,  87,  19,  83,  90,
    91,  92,  93,  94,  95,  20,  84,  98,  99, 100, 101, 102, 103,
    22,  86, 106, 107, 108, 109, 110, 111,  21,  85, 106, 115, 116,
    117, 118, 119,  23,  87, 122, 123, 124, 125, 126, 127,   1,  18,
    10,  19,  20,  22,  21,  23,  10,  73,  81,  83,  84,  86,  85,
    87,   9,  73,  73,  90,  98, 106, 106, 122,  11,  75,  83,  91,
    99, 107, 115, 123,  10,  76,  84,  92, 100, 108, 116, 124,  14,
    77,  85,  93, 101, 109, 117, 125,  11,  77,  86,  94, 102, 110,
    118, 126,  15,  79,  87,  95, 103, 111, 119, 127,   3,  19,  11,
    27,  21,  30,  29,  31,  19,  90,  83,  91,  92,  94,  93,  95,
    11,  83,  75,  91,  99, 115, 107, 123,  27,  91,  91, 219, 220,
    221, 221, 223,  21,  92,  99, 220, 228, 229, 230, 231,  30,  94,
    115, 221, 229, 237, 238, 239,  29,  93, 107, 221, 230, 238, 246,
    247,  31,  95, 123, 223, 231, 239, 247, 255,   1,  20,  10,  21,
    18,  22,  19,  23,  20,  98,  84,  99, 100, 102, 101, 103,  10,
    84,  76,  92, 100, 116, 108, 124,  21,  99,  92, 220, 228, 230,
    229, 231,  18, 100, 100, 228, 292, 293, 293, 295,  22, 102, 116,
    230, 293, 301, 302, 303,  19, 101, 108, 229, 293, 302, 310, 311,
    23, 103, 124, 231, 295, 303, 311, 319,   3,  21,  11,  29,  19,
    30,  27,  31,  22, 106,  86, 107, 108, 110, 109, 111,  14,  85,
    77,  93, 101, 117, 109, 125,  30, 115,  94, 221, 229, 238, 237,
    239,  22, 116, 102, 230, 293, 302, 301, 303,  54, 118, 118, 246,
    310, 365, 365, 367,  30, 117, 110, 238, 302, 373, 365, 375,  55,
    119, 126, 247, 311, 375, 382, 383,   3,  22,  14,  30,  22,  54,
    30,  55,  21, 106,  85, 115, 116, 118, 117, 119,  11,  86,  77,
    94, 102, 118, 110, 126,  29, 107,  93, 221, 230, 246, 238, 247,
    19, 108, 101, 229, 293, 310, 302, 311,  30, 110, 117, 238, 302,
    365, 373, 375,  27, 109, 109, 237, 301, 365, 365, 382,  31, 111,
    125, 239, 303, 367, 375, 383,   7,  23,  15,  31,  23,  55,  31,
    63,  23, 122,  87, 123, 124, 126, 125, 127,  15,  87,  79,  95,
    103, 119, 111, 127,  31, 123,  95, 223, 231, 247, 239, 255,  23,
    124, 103, 231, 295, 311, 303, 319,  55, 126, 119, 247, 311, 382,
    375, 383,  31, 125, 111, 239, 303, 375, 367, 383,  63, 127, 127,
    255, 319, 383, 383, 511,   1,  10,  10,  14,   9,  11,  11,  15,
    18,  73,  76,  77,  73,  75,  77,  79,  20,  84, 100, 101,  98,
    99, 102, 103,  22,  86, 108, 109, 106, 107, 110, 111,  10,  81,
    84,  85,  73,  83,  86,  87,  19,  83,  92,  93,  90,  91,  94,
    95,  21,  85, 116, 117, 106, 115, 118, 119,  23,  87, 124, 125,
    122, 123, 126, 127,  18,  76,  73,  77,  73,  77,  75,  79, 292,
    585, 585, 587, 585, 587, 587, 591, 100, 593, 594, 595, 596, 597,
    598, 599, 293, 601, 602, 603, 604, 605, 606, 607, 100, 593, 596,
    597, 594, 595, 598, 599, 293, 601, 604, 605, 602, 603, 606, 607,
    228, 625, 626, 627, 626, 627, 630, 631, 295, 633, 634, 635, 634,
    635, 638, 639,  20, 100,  84, 101,  98, 102,  99, 103, 100, 594,
    593, 595, 596, 598, 597, 599,  98, 596, 596, 659, 660, 661, 661,
    663, 102, 598, 666, 667, 661, 669, 670, 671,  84, 593, 674, 675,
    596, 666, 678, 679, 101, 595, 675, 683, 659, 667, 686, 687,  99,
    597, 678, 686, 661, 670, 694, 695, 103, 599, 679, 687, 663, 671,
    695, 703,  22, 108,  86, 109, 106, 110, 107, 111, 293, 602, 601,
    603, 604, 606, 605, 607, 102, 666, 598, 667, 661, 670, 669, 671,
    301, 729, 729, 731, 732, 733, 733, 735, 116, 737, 678, 739, 626,
    741, 742, 743, 302, 745, 746, 747, 748, 749, 750, 751, 230, 753,
    742, 755, 756, 757, 758, 759, 303, 761, 762, 763, 764, 765, 766,
    767,  10,  84,  81,  85,  73,  86,  83,  87, 100, 596, 593, 597,
    594, 598, 595, 599,  84, 674, 593, 675, 596, 678, 666, 679, 116,
    678, 737, 739, 626, 742, 741, 743,  76, 593, 593, 625, 585, 601,
    601, 633, 108, 666, 737, 753, 602, 729, 745, 761,  92, 675, 737,
    819, 604, 746, 822, 823, 124, 679, 826, 827, 634, 762, 830, 831,
    19,  92,  83,  93,  90,  94,  91,  95, 293, 604, 601, 605, 602,
    606, 603, 607, 101, 675, 595, 683, 659, 686, 667, 687, 302, 746,
    745, 747, 748, 750, 749, 751, 108, 737, 666, 753, 602, 745, 729,
    761, 310, 822, 822, 875, 876, 877, 877, 879, 229, 819, 741, 883,
    748, 885, 886, 887, 311, 823, 830, 891, 892, 893, 894, 895,  21,
    116,  85, 117, 106, 118, 115, 119, 228, 626, 625, 627, 626, 630,
    627, 631,  99, 678, 597, 686, 661, 694, 670, 695, 230, 742, 753,
    755, 756, 758, 757, 759,  92, 737, 675, 819, 604, 822, 746, 823,
    229, 741, 819, 883, 748, 886, 885, 887, 220, 739, 739, 947, 732,
    949, 949, 951, 231, 743, 827, 955, 764, 957, 958, 959,  23, 124,
    87, 125, 122, 126, 123, 127, 295, 634, 633, 635, 634, 638, 635,
    639, 103, 679, 599, 687, 663, 695, 671, 703, 303, 762, 761, 763,
    764, 766, 765, 767, 124, 826, 679, 827, 634, 830, 762, 831, 311,
    830, 823, 891, 892, 894, 893, 895, 231, 827, 743, 955, 764, 958,
    957, 959, 319, 831, 831, 1019, 1020, 1021, 1021, 1023,   1,  18,  20,
    22,  10,  19,  21,  23,  10,  73,  84,  86,  81,  83,  85,  87,
    10,  76, 100, 108,  84,  92, 116, 124,  14,  77, 101, 109,  85,
    93, 117, 125,   9,  73,  98, 106,  73,  90, 106, 122,  11,  75,
    99, 107,  83,  91, 115, 123,  11,  77, 102, 110,  86,  94, 118,
    126,  15,  79, 103, 111,  87,  95, 119, 127,  20, 100,  98, 102,
    84, 101,  99, 103, 100, 594, 596, 598, 593, 595, 597, 599,  84,
    593, 596, 666, 674, 675, 678, 679, 101, 595, 659, 667, 675, 683,
    686, 687,  98, 596, 660, 661, 596, 659, 661, 663, 102, 598, 661,
    669, 666, 667, 670, 671,  99, 597, 661, 670, 678, 686, 694, 695,
    103, 599, 663, 671, 679, 687, 695, 703,  18, 292, 100, 293, 100,
    293, 228, 295,  76, 585, 593, 601, 593, 601, 625, 633,  73, 585,
    594, 602, 596, 604, 626, 634,  77, 587, 595, 603, 597, 605, 627,
    635,  73, 585, 596, 604, 594, 602, 626, 634,  77, 587, 597, 605,
    595, 603, 627, 635,  75, 587, 598, 606, 598, 606, 630, 638,  79,
    591, 599, 607, 599, 607, 631, 639,  22, 293, 102, 301, 116, 302,
    230, 303, 108, 602, 666, 729, 737, 745, 753, 761,  86, 601, 598,
    729, 678, 746, 742, 762, 109, 603, 667, 731, 739, 747, 755, 763,
    106, 604, 661, 732, 626, 748, 756, 764, 110, 606, 670, 733, 741,
    749, 757, 765, 107, 605, 669, 733, 742, 750, 758, 766, 111, 607,
    671, 735, 743, 751, 759, 767,  10, 100,  84, 116,  76, 108,  92,
    124,  84, 596, 674, 678, 593, 666, 675, 679,  81, 593, 593, 737,
    593, 737, 737, 826,  85, 597, 675, 739, 625, 753, 819, 827,  73,
    594, 596, 626, 585, 602, 604, 634,  86, 598, 678, 742, 601, 729,
    746, 762,  83, 595, 666, 741, 601, 745, 822, 830,  87, 599, 679,
    743, 633, 761, 823, 831,  21, 228,  99, 230,  92, 229, 220, 231,
    116, 626, 678, 742, 737, 741, 739, 743,  85, 625, 597, 753, 675,
    819, 739, 827, 117, 627, 686, 755, 819, 883, 947, 955, 106, 626,
    661, 756, 604, 748, 732, 764, 118, 630, 694, 758, 822, 886, 949,
    957, 115, 627, 670, 757, 746, 885, 949, 958, 119, 631, 695, 759,
    823, 887, 951, 959,  19, 293, 101, 302, 108, 310, 229, 311,  92,
    604, 675, 746, 737, 822, 819, 823,  83, 601, 595, 745, 666, 822,
    741, 830,  93, 605, 683, 747, 753, 875, 883, 891,  90, 602, 659,
    748, 602, 876, 748, 892,  94, 606, 686, 750, 745, 877, 885, 893,
    91, 603, 667, 749, 729, 877, 886, 894,  95, 607, 687, 751, 761,
    879, 887, 895,  23, 295, 103, 303, 124, 311, 231, 319, 124, 634,
    679, 762, 826, 830, 827, 831,  87, 633, 599, 761, 679, 823, 743,
    831, 125, 635, 687, 763, 827, 891, 955, 1019, 122, 634, 663, 764,
    634, 892, 764, 1020, 126, 638, 695, 766, 830, 894, 958, 1021, 123,
    635, 671, 765, 762, 893, 957, 1021, 127, 639, 703, 767, 831, 895,
    959, 1023,   3,  19,  21,  30,  11,  27,  29,  31,  19,  90,  92,
    94,  83,  91,  93,  95,  21,  92, 228, 229,  99, 220, 230, 231,
    30,  94, 229, 237, 115, 221, 238, 239,  11,  83,  99, 115,  75,
    91, 107, 123,  27,  91, 220, 221,  91, 219, 221, 223,  29,  93,
    230, 238, 107, 221, 246, 247,  31,  95, 231, 239, 123, 223, 247,
    255,  22, 108, 106, 110,  86, 109, 107, 111, 293, 602, 604, 606,
    601, 603, 605, 607, 116, 737, 626, 741, 678, 739, 742, 743, 302,
    745, 748, 749, 746, 747, 750, 751, 102, 666, 661, 670, 598, 667,
    669, 671, 301, 729, 732, 733, 729, 731, 733, 735, 230, 753, 756,
    757, 742, 755, 758, 759, 303, 761, 764, 765, 762, 763, 766, 767,
    22, 293, 116, 302, 102, 301, 230, 303, 108, 602, 737, 745, 666,
    729, 753, 761, 106, 604, 626, 748, 661, 732, 756, 764, 110, 606,
    741, 749, 670, 733, 757, 765,  86, 601, 678, 746, 598, 729, 742,
    762, 109, 603, 739, 747, 667, 731, 755, 763, 107, 605, 742, 750,
    669, 733, 758, 766, 111, 607, 743, 751, 671, 735, 759, 767,  54,
    310, 118, 365, 118, 365, 246, 367, 310, 876, 822, 877, 822, 877,
    875, 879, 118, 822, 630, 886, 694, 949, 758, 957, 365, 877, 886,
    1755, 949, 1757, 1758, 1759, 118, 822, 694, 949, 630, 886, 758, 957,
    365, 877, 949, 1757, 886, 1755, 1758, 1759, 246, 875, 758, 1758, 758,
    1758, 1782, 1783, 367, 879, 957, 1759, 957, 1759, 1783, 1791,  14, 101,
    85, 117,  77, 109,  93, 125, 101, 659, 675, 686, 595, 667, 683,
    687,  85, 675, 625, 819, 597, 739, 753, 827, 117, 686, 819, 947,
    627, 755, 883, 955,  77, 595, 597, 627, 587, 603, 605, 635, 109,
    667, 739, 755, 603, 731, 747, 763,  93, 683, 753, 883, 605, 747,
    875, 891, 125, 687, 827, 955, 635, 763, 891, 1019,  30, 229, 115,
    238,  94, 237, 221, 239, 302, 748, 746, 750, 745, 749, 747, 751,
    117, 819, 627, 883, 686, 947, 755, 955, 373, 885, 885, 1883, 885,
    1883, 1883, 1887, 110, 741, 670, 757, 606, 749, 733, 765, 365, 886,
    949, 1758, 877, 1755, 1757, 1759, 238, 883, 757, 1907, 750, 1883, 1758,
    1911, 375, 887, 958, 1911, 893, 1917, 1918, 1919,  30, 302, 117, 373,
    110, 365, 238, 375, 229, 748, 819, 885, 741, 886, 883, 887, 115,
    746, 627, 885, 670, 949, 757, 958, 238, 750, 883, 1883, 757, 1758,
    1907, 1911,  94, 745, 686, 885, 606, 877, 750, 893, 237, 749, 947,
    1883, 749, 1755, 1883, 1917, 221, 747, 755, 1883, 733, 1757, 1758, 1918,
    239, 751, 955, 1887, 765, 1759, 1911, 1919,  55, 311, 119, 375, 126,
    382, 247, 383, 311, 892, 823, 893, 830, 894, 891, 895, 119, 823,
    631, 887, 695, 951, 759, 959, 375, 893, 887, 1917, 958, 1918, 1911,
    1919, 126, 830, 695, 958, 638, 894, 766, 1021, 382, 894, 951, 1918,
    894, 2029, 1918, 2031, 247, 891, 759, 1911, 766, 1918, 1783, 2039, 383,
    895, 959, 1919, 1021, 2031, 2039, 2047,   1,  20,  18,  22,  10,  21,
    19,  23,  20,  98, 100, 102,  84,  99, 101, 103,  18, 100, 292,
    293, 100, 228, 293, 295,  22, 102, 293, 301, 116, 230, 302, 303,
    10,  84, 100, 116,  76,  92, 108, 124,  21,  99, 228, 230,  92,
    220, 229, 231,  19, 101, 293, 302, 108, 229, 310, 311,  23, 103,
    295, 303, 124, 231, 311, 319,  10,  84,  73,  86,  81,  85,  83,
    87, 100, 596, 594, 598, 593, 597, 595, 599,  76, 593, 585, 601,
    593, 625, 601, 633, 108, 666, 602, 729, 737, 753, 745, 761,  84,
    674, 596, 678, 593, 675, 666, 679, 116, 678, 626, 742, 737, 739,
    741, 743,  92, 675, 604, 746, 737, 819, 822, 823, 124, 679, 634,
    762, 826, 827, 830, 831,  10, 100,  76, 108,  84, 116,  92, 124,
    84, 596, 593, 666, 674, 678, 675, 679,  73, 594, 585, 602, 596,
    626, 604, 634,  86, 598, 601, 729, 678, 742, 746, 762,  81, 593,
    593, 737, 593, 737, 737, 826,  85, 597, 625, 753, 675, 739, 819,
    827,  83, 595, 601, 745, 666, 741, 822, 830,  87, 599, 633, 761,
    679, 743, 823, 831,  14, 101,  77, 109,  85, 117,  93, 125, 101,
    659, 595, 667, 675, 686, 683, 687,  77, 595, 587, 603, 597, 627,
    605, 635, 109, 667, 603, 731, 739, 755, 747, 763,  85, 675, 597,
    739, 625, 819, 753, 827, 117, 686, 627, 755, 819, 947, 883, 955,
    93, 683, 605, 747, 753, 883, 875, 891, 125, 687, 635, 763, 827,
    955, 891, 1019,   9,  98,  73, 106,  73, 106,  90, 122,  98, 660,
    596, 661, 596, 661, 659, 663,  73, 596, 585, 604, 594, 626, 602,
    634, 106, 661, 604, 732, 626, 756, 748, 764,  73, 596, 594, 626,
    585, 604, 602, 634, 106, 661, 626, 756, 604, 732, 748, 764,  90,
    659, 602, 748, 602, 748, 876, 892, 122, 663, 634, 764, 634, 764,
    892, 1020,  11,  99,  75, 107,  83, 115,  91, 123, 102, 661, 598,
    669, 666, 670, 667, 671,  77, 597, 587, 605, 595, 627, 603, 635,
    110, 670, 606, 733, 741, 757, 749, 765,  86, 678, 598, 742, 601,
    746, 729, 762, 118, 694, 630, 758, 822, 949, 886, 957,  94, 686,
    606, 750, 745, 885, 877, 893, 126, 695, 638, 766, 830, 958, 894,
    1021,  11, 102,  77, 110,  86, 118,  94, 126,  99, 661, 597, 670,
    678, 694, 686, 695,  75, 598, 587, 606, 598, 630, 606, 638, 107,
    669, 605, 733, 742, 758, 750, 766,  83, 666, 595, 741, 601, 822,
    745, 830, 115, 670, 627, 757, 746, 949, 885, 958,  91, 667, 603,
    749, 729, 886, 877, 894, 123, 671, 635, 765, 762, 957, 893, 1021,
    15, 103,  79, 111,  87, 119,  95, 127, 103, 663, 599, 671, 679,
    695, 687, 703,  79, 599, 591, 607, 599, 631, 607, 639, 111, 671,
    607, 735, 743, 759, 751, 767,  87, 679, 599, 743, 633, 823, 761,
    831, 119, 695, 631, 759, 823, 951, 887, 959,  95, 687, 607, 751,
    761, 887, 879, 895, 127, 703, 639, 767, 831, 959, 895, 1023,   3,
    21,  19,  30,  11,  29,  27,  31,  22, 106, 108, 110,  86, 107,
    109, 111,  22, 116, 293, 302, 102, 230, 301, 303,  54, 118, 310,
    365, 118, 246, 365, 367,  14,  85, 101, 117,  77,  93, 109, 125,
    30, 115, 229, 238,  94, 221, 237, 239,  30, 117, 302, 373, 110,
    238, 365, 375,  55, 119, 311, 375, 126, 247, 382, 383,  19,  92,
    90,  94,  83,  93,  91,  95, 293, 604, 602, 606, 601, 605, 603,
    607, 108, 737, 602, 745, 666, 753, 729, 761, 310, 822, 876, 877,
    822, 875, 877, 879, 101, 675, 659, 686, 595, 683, 667, 687, 302,
    746, 748, 750, 745, 747, 749, 751, 229, 819, 748, 885, 741, 883,
    886, 887, 311, 823, 892, 893, 830, 891, 894, 895,  21, 228,  92,
    229,  99, 230, 220, 231, 116, 626, 737, 741, 678, 742, 739, 743,
    106, 626, 604, 748, 661, 756, 732, 764, 118, 630, 822, 886, 694,
    758, 949, 957,  85, 625, 675, 819, 597, 753, 739, 827, 117, 627,
    819, 883, 686, 755, 947, 955, 115, 627, 746, 885, 670, 757, 949,
    958, 119, 631, 823, 887, 695, 759, 951, 959,  30, 229,  94, 237,
    115, 238, 221, 239, 302, 748, 745, 749, 746, 750, 747, 751, 110,
    741, 606, 749, 670, 757, 733, 765, 365, 886, 877, 1755, 949, 1758,
    1757, 1759, 117, 819, 686, 947, 627, 883, 755, 955, 373, 885, 885,
    1883, 885, 1883, 1883, 1887, 238, 883, 750, 1883, 757, 1907, 1758, 1911,
    375, 887, 893, 1917, 958, 1911, 1918, 1919,  11,  99,  83, 115,  75,
    107,  91, 123, 102, 661, 666, 670, 598, 669, 667, 671,  86, 678,
    601, 746, 598, 742, 729, 762, 118, 694, 822, 949, 630, 758, 886,
    957,  77, 597, 595, 627, 587, 605, 603, 635, 110, 670, 741, 757,
    606, 733, 749, 765,  94, 686, 745, 885, 606, 750, 877, 893, 126,
    695, 830, 958, 638, 766, 894, 1021,  27, 220,  91, 221,  91, 221,
    219, 223, 301, 732, 729, 733, 729, 733, 731, 735, 109, 739, 603,
    747, 667, 755, 731, 763, 365, 949, 877, 1757, 886, 1758, 1755, 1759,
    109, 739, 667, 755, 603, 747, 731, 763, 365, 949, 886, 1758, 877,
    1757, 1755, 1759, 237, 947, 749, 1883, 749, 1883, 1755, 1917, 382, 951,
    894, 1918, 894, 1918, 2029, 2031,  29, 230,  93, 238, 107, 246, 221,
    247, 230, 756, 753, 757, 742, 758, 755, 759, 107, 742, 605, 750,
    669, 758, 733, 766, 246, 758, 875, 1758, 758, 1782, 1758, 1783,  93,
    753, 683, 883, 605, 875, 747, 891, 238, 757, 883, 1907, 750, 1758,
    1883, 1911, 221, 755, 747, 1883, 733, 1758, 1757, 1918, 247, 759, 891,
    1911, 766, 1783, 1918, 2039,  31, 231,  95, 239, 123, 247, 223, 255,
    303, 764, 761, 765, 762, 766, 763, 767, 111, 743, 607, 751, 671,
    759, 735, 767, 367, 957, 879, 1759, 957, 1783, 1759, 1791, 125, 827,
    687, 955, 635, 891, 763, 1019, 375, 958, 887, 1911, 893, 1918, 1917,
    1919, 239, 955, 751, 1887, 765, 1911, 1759, 1919, 383, 959, 895, 1919,
    1021, 2039, 2031, 2047,   3,  22,  22,  54,  14,  30,  30,  55,  21,
    106, 116, 118,  85, 115, 117, 119,  19, 108, 293, 310, 101, 229,
    302, 311,  30, 110, 302, 365, 117, 238, 373, 375,  11,  86, 102,
    118,  77,  94, 110, 126,  29, 107, 230, 246,  93, 221, 238, 247,
    27, 109, 301, 365, 109, 237, 365, 382,  31, 111, 303, 367, 125,
    239, 375, 383,  21, 116, 106, 118,  85, 117, 115, 119, 228, 626,
    626, 630, 625, 627, 627, 631,  92, 737, 604, 822, 675, 819, 746,
    823, 229, 741, 748, 886, 819, 883, 885, 887,  99, 678, 661, 694,
    597, 686, 670, 695, 230, 742, 756, 758, 753, 755, 757, 759, 220,
    739, 732, 949, 739, 947, 949, 951, 231, 743, 764, 957, 827, 955,
    958, 959,  19, 293, 108, 310, 101, 302, 229, 311,  92, 604, 737,
    822, 675, 746, 819, 823,  90, 602, 602, 876, 659, 748, 748, 892,
    94, 606, 745, 877, 686, 750, 885, 893,  83, 601, 666, 822, 595,
    745, 741, 830,  93, 605, 753, 875, 683, 747, 883, 891,  91, 603,
    729, 877, 667, 749, 886, 894,  95, 607, 761, 879, 687, 751, 887,
    895,  30, 302, 110, 365, 117, 373, 238, 375, 229, 748, 741, 886,
    819, 885, 883, 887,  94, 745, 606, 877, 686, 885, 750, 893, 237,
    749, 749, 1755, 947, 1883, 1883, 1917, 115, 746, 670, 949, 627, 885,
    757, 958, 238, 750, 757, 1758, 883, 1883, 1907, 1911, 221, 747, 733,
    1757, 755, 1883, 1758, 1918, 239, 751, 765, 1759, 955, 1887, 1911, 1919,
    11, 102,  86, 118,  77, 110,  94, 126,  99, 661, 678, 694, 597,
    670, 686, 695,  83, 666, 601, 822, 595, 741, 745, 830, 115, 670,
    746, 949, 627, 757, 885, 958,  75, 598, 598, 630, 587, 606, 606,
    638, 107, 669, 742, 758, 605, 733, 750, 766,  91, 667, 729, 886,
    603, 749, 877, 894, 123, 671, 762, 957, 635, 765, 893, 1021,  29,
    230, 107, 246,  93, 238, 221, 247, 230, 756, 742, 758, 753, 757,
    755, 759,  93, 753, 605, 875, 683, 883, 747, 891, 238, 757, 750,
    1758, 883, 1907, 1883, 1911, 107, 742, 669, 758, 605, 750, 733, 766,
    246, 758, 758, 1782, 875, 1758, 1758, 1783, 221, 755, 733, 1758, 747,
    1883, 1757, 1918, 247, 759, 766, 1783, 891, 1911, 1918, 2039,  27, 301,
    109, 365, 109, 365, 237, 382, 220, 732, 739, 949, 739, 949, 947,
    951,  91, 729, 603, 877, 667, 886, 749, 894, 221, 733, 747, 1757,
    755, 1758, 1883, 1918,  91, 729, 667, 886, 603, 877, 749, 894, 221,
    733, 755, 1758, 747, 1757, 1883, 1918, 219, 731, 731, 1755, 731, 1755,
    1755, 2029, 223, 735, 763, 1759, 763, 1759, 1917, 2031,  31, 303, 111,
    367, 125, 375, 239, 383, 231, 764, 743, 957, 827, 958, 955, 959,
    95, 761, 607, 879, 687, 887, 751, 895, 239, 765, 751, 1759, 955,
    1911, 1887, 1919, 123, 762, 671, 957, 635, 893, 765, 1021, 247, 766,
    759, 1783, 891, 1918, 1911, 2039, 223, 763, 735, 1759, 763, 1917, 1759,
    2031, 255, 767, 767, 1791, 1019, 1919, 1919, 2047,   7,  23,  23,  55,
    15,  31,  31,  63,  23, 122, 124, 126,  87, 123, 125, 127,  23,
    124, 295, 311, 103, 231, 303, 319,  55, 126, 311, 382, 119, 247,
    375, 383,  15,  87, 103, 119,  79,  95, 111, 127,  31, 123, 231,
    247,  95, 223, 239, 255,  31, 125, 303, 375, 111, 239, 367, 383,
    63, 127, 319, 383, 127, 255, 383, 511,  23, 124, 122, 126,  87,
    125, 123, 127, 295, 634, 634, 638, 633, 635, 635, 639, 124, 826,
    634, 830, 679, 827, 762, 831, 311, 830, 892, 894, 823, 891, 893,
    895, 103, 679, 663, 695, 599, 687, 671, 703, 303, 762, 764, 766,
    761, 763, 765, 767, 231, 827, 764, 958, 743, 955, 957, 959, 319,
    831, 1020, 1021, 831, 1019, 1021, 1023,  23, 295, 124, 311, 103, 303,
    231, 319, 124, 634, 826, 830, 679, 762, 827, 831, 122, 634, 634,
    892, 663, 764, 764, 1020, 126, 638, 830, 894, 695, 766, 958, 1021,
    87, 633, 679, 823, 599, 761, 743, 831, 125, 635, 827, 891, 687,
    763, 955, 1019, 123, 635, 762, 893, 671, 765, 957, 1021, 127, 639,
    831, 895, 703, 767, 959, 1023,  55, 311, 126, 382, 119, 375, 247,
    383, 311, 892, 830, 894, 823, 893, 891, 895, 126, 830, 638, 894,
    695, 958, 766, 1021, 382, 894, 894, 2029, 951, 1918, 1918, 2031, 119,
    823, 695, 951, 631, 887, 759, 959, 375, 893, 958, 1918, 887, 1917,
    1911, 1919, 247, 891, 766, 1918, 759, 1911, 1783, 2039, 383, 895, 1021,
    2031, 959, 1919, 2039, 2047,  15, 103,  87, 119,  79, 111,  95, 127,
    103, 663, 679, 695, 599, 671, 687, 703,  87, 679, 633, 823, 599,
    743, 761, 831, 119, 695, 823, 951, 631, 759, 887, 959,  79, 599,
    599, 631, 591, 607, 607, 639, 111, 671, 743, 759, 607, 735, 751,
    767,  95, 687, 761, 887, 607, 751, 879, 895, 127, 703, 831, 959,
    639, 767, 895, 1023,  31, 231, 123, 247,  95, 239, 223, 255, 303,
    764, 762, 766, 761, 765, 763, 767, 125, 827, 635, 891, 687, 955,
    763, 1019, 375, 958, 893, 1918, 887, 1911, 1917, 1919, 111, 743, 671,
    759, 607, 751, 735, 767, 367, 957, 957, 1783, 879, 1759, 1759, 1791,
    239, 955, 765, 1911, 751, 1887, 1759, 1919, 383, 959, 1021, 2039, 895,
    1919, 2031, 2047,  31, 303, 125, 375, 111, 367, 239, 383, 231, 764,
    827, 958, 743, 957, 955, 959, 123, 762, 635, 893, 671, 957, 765,
    1021, 247, 766, 891, 1918, 759, 1783, 1911, 2039,  95, 761, 687, 887,
    607, 879, 751, 895, 239, 765, 955, 1911, 751, 1759, 1887, 1919, 223,
    763, 763, 1917, 735, 1759, 1759, 2031, 255, 767, 1019, 1919, 767, 1791,
    1919, 2047,  63, 319, 127, 383, 127, 383, 255, 511, 319, 1020, 831,
    1021, 831, 1021, 1019, 1023, 127, 831, 639, 895, 703, 959, 767, 1023,
    383, 1021, 895, 2031, 959, 2039, 1919, 2047, 127, 831, 703, 959, 639,
    895, 767, 1023, 383, 1021, 959, 2039, 895, 2031, 1919, 2047, 255, 1019,
    767, 1919, 767, 1919, 1791, 2047, 511, 1023, 1023, 2047, 1023, 2047, 2047,
    4095
};

const unsigned int igraph_i_isoclass_4_idx[] = {
    0, 8, 64, 512, 1, 0, 128, 1024, 2, 16, 0, 2048, 4, 32, 256, 0
};

const unsigned int igraph_i_isoclass_3u[] = { 0, 1, 1, 3, 1, 3, 3, 7 };

const unsigned int igraph_i_isoclass_3u_idx[] = { 0, 1, 2, 1, 0, 4, 2, 4, 0 };

const unsigned int igraph_i_isoclass_4u[] = {
    0, 1, 1, 3, 1, 3, 3, 7, 1, 3, 3, 11, 12, 13, 13, 15, 1, 3, 12, 13, 3, 11, 13, 15, 3, 7,
    13, 15, 13, 15, 30, 31, 1, 12, 3, 13, 3, 13, 11, 15, 3, 13, 7, 15, 13, 30, 15, 31, 3, 13, 13, 30,
    7, 15, 15, 31, 11, 15, 15, 31, 15, 31, 31, 63
};

const unsigned int igraph_i_isoclass_4u_idx[] = {
    0, 1, 2, 8, 1, 0, 4, 16, 2, 4, 0, 32, 8, 16, 32, 0
};

const unsigned int igraph_i_isoclass2_3[] = {
    0, 1, 1, 2, 1, 3, 4, 5, 1, 4, 6, 7, 2, 5, 7, 8, 1, 4, 3, 5, 6, 9, 9, 10, 4, 11,
    9, 12, 7, 12, 13, 14, 1, 6, 4, 7, 4, 9, 11, 12, 3, 9, 9, 13, 5, 10, 12, 14, 2, 7, 5, 8,
    7, 13, 12, 14, 5, 12, 10, 14, 8, 14, 14, 15
};

const unsigned int igraph_i_isoclass2_3u[] = {
    0, 1, 1, 2, 1, 2, 2, 3
};

const unsigned int igraph_i_isoclass2_4u[] = {
    0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 4, 5, 6, 6, 7, 1, 2, 5, 6, 2, 4, 6, 7, 2, 3,
    6, 7, 6, 7, 8, 9, 1, 5, 2, 6, 2, 6, 4, 7, 2, 6, 3, 7, 6, 8, 7, 9, 2, 6, 6, 8,
    3, 7, 7, 9, 4, 7, 7, 9, 7, 9, 9, 10
};

const unsigned int igraph_i_isoclass2_4[] = {
    0,  1,  1,  2,  1,  2,  2,  3,  1,  4,  5,  6,  5,  6,  7,  8,  1,  5,  9, 10,
    11, 12, 13, 14,  2,  6, 10, 15, 12, 16, 17, 18,  1,  5, 11, 12,  9, 10, 13, 14,
    2,  6, 12, 16, 10, 15, 17, 18,  2,  7, 13, 17, 13, 17, 19, 20,  3,  8, 14, 18,
    14, 18, 20, 21,  1,  5,  4,  6,  5,  7,  6,  8,  9, 22, 22, 23, 24, 25, 25, 26,
    5, 27, 22, 28, 29, 30, 31, 32, 10, 28, 33, 34, 35, 36, 37, 38, 11, 29, 39, 40,
    41, 42, 43, 44, 13, 31, 45, 46, 47, 48, 49, 50, 12, 30, 45, 51, 52, 53, 54, 55,
    14, 32, 56, 57, 58, 59, 60, 61,  1,  9,  5, 10, 11, 13, 12, 14,  5, 22, 27, 28,
    29, 31, 30, 32,  4, 22, 22, 33, 39, 45, 45, 56,  6, 23, 28, 34, 40, 46, 51, 57,
    5, 24, 29, 35, 41, 47, 52, 58,  7, 25, 30, 36, 42, 48, 53, 59,  6, 25, 31, 37,
    43, 49, 54, 60,  8, 26, 32, 38, 44, 50, 55, 61,  2, 10,  6, 15, 12, 17, 16, 18,
    10, 33, 28, 34, 35, 37, 36, 38,  6, 28, 23, 34, 40, 51, 46, 57, 15, 34, 34, 62,
    63, 64, 64, 65, 12, 35, 40, 63, 66, 67, 68, 69, 17, 37, 51, 64, 67, 70, 71, 72,
    16, 36, 46, 64, 68, 71, 73, 74, 18, 38, 57, 65, 69, 72, 74, 75,  1, 11,  5, 12,
    9, 13, 10, 14, 11, 39, 29, 40, 41, 43, 42, 44,  5, 29, 24, 35, 41, 52, 47, 58,
    12, 40, 35, 63, 66, 68, 67, 69,  9, 41, 41, 66, 76, 77, 77, 78, 13, 43, 52, 68,
    77, 79, 80, 81, 10, 42, 47, 67, 77, 80, 82, 83, 14, 44, 58, 69, 78, 81, 83, 84,
    2, 12,  6, 16, 10, 17, 15, 18, 13, 45, 31, 46, 47, 49, 48, 50,  7, 30, 25, 36,
    42, 53, 48, 59, 17, 51, 37, 64, 67, 71, 70, 72, 13, 52, 43, 68, 77, 80, 79, 81,
    19, 54, 54, 73, 82, 85, 85, 86, 17, 53, 49, 71, 80, 87, 85, 88, 20, 55, 60, 74,
    83, 88, 89, 90,  2, 13,  7, 17, 13, 19, 17, 20, 12, 45, 30, 51, 52, 54, 53, 55,
    6, 31, 25, 37, 43, 54, 49, 60, 16, 46, 36, 64, 68, 73, 71, 74, 10, 47, 42, 67,
    77, 82, 80, 83, 17, 49, 53, 71, 80, 85, 87, 88, 15, 48, 48, 70, 79, 85, 85, 89,
    18, 50, 59, 72, 81, 86, 88, 90,  3, 14,  8, 18, 14, 20, 18, 21, 14, 56, 32, 57,
    58, 60, 59, 61,  8, 32, 26, 38, 44, 55, 50, 61, 18, 57, 38, 65, 69, 74, 72, 75,
    14, 58, 44, 69, 78, 83, 81, 84, 20, 60, 55, 74, 83, 89, 88, 90, 18, 59, 50, 72,
    81, 88, 86, 90, 21, 61, 61, 75, 84, 90, 90, 91,  1,  5,  5,  7,  4,  6,  6,  8,
    9, 22, 24, 25, 22, 23, 25, 26, 11, 29, 41, 42, 39, 40, 43, 44, 13, 31, 47, 48,
    45, 46, 49, 50,  5, 27, 29, 30, 22, 28, 31, 32, 10, 28, 35, 36, 33, 34, 37, 38,
    12, 30, 52, 53, 45, 51, 54, 55, 14, 32, 58, 59, 56, 57, 60, 61,  9, 24, 22, 25,
    22, 25, 23, 26, 76, 92, 92, 93, 92, 93, 93, 94, 41, 95, 96, 97, 98, 99, 100, 101,
    77, 102, 103, 104, 105, 106, 107, 108, 41, 95, 98, 99, 96, 97, 100, 101, 77, 102, 105, 106,
    103, 104, 107, 108, 66, 109, 110, 111, 110, 111, 112, 113, 78, 114, 115, 116, 115, 116, 117, 118,
    11, 41, 29, 42, 39, 43, 40, 44, 41, 96, 95, 97, 98, 100, 99, 101, 39, 98, 98, 119,
    120, 121, 121, 122, 43, 100, 123, 124, 121, 125, 126, 127, 29, 95, 128, 129, 98, 123, 130, 131,
    42, 97, 129, 132, 119, 124, 133, 134, 40, 99, 130, 133, 121, 126, 135, 136, 44, 101, 131, 134,
    122, 127, 136, 137, 13, 47, 31, 48, 45, 49, 46, 50, 77, 103, 102, 104, 105, 107, 106, 108,
    43, 123, 100, 124, 121, 126, 125, 127, 79, 138, 138, 139, 140, 141, 141, 142, 52, 143, 130, 144,
    110, 145, 146, 147, 80, 148, 149, 150, 151, 152, 153, 154, 68, 155, 146, 156, 157, 158, 159, 160,
    81, 161, 162, 163, 164, 165, 166, 167,  5, 29, 27, 30, 22, 31, 28, 32, 41, 98, 95, 99,
    96, 100, 97, 101, 29, 128, 95, 129, 98, 130, 123, 131, 52, 130, 143, 144, 110, 146, 145, 147,
    24, 95, 95, 109, 92, 102, 102, 114, 47, 123, 143, 155, 103, 138, 148, 161, 35, 129, 143, 168,
    105, 149, 169, 170, 58, 131, 171, 172, 115, 162, 173, 174, 10, 35, 28, 36, 33, 37, 34, 38,
    77, 105, 102, 106, 103, 107, 104, 108, 42, 129, 97, 132, 119, 133, 124, 134, 80, 149, 148, 150,
    151, 153, 152, 154, 47, 143, 123, 155, 103, 148, 138, 161, 82, 169, 169, 175, 176, 177, 177, 178,
    67, 168, 145, 179, 151, 180, 181, 182, 83, 170, 173, 183, 184, 185, 186, 187, 12, 52, 30, 53,
    45, 54, 51, 55, 66, 110, 109, 111, 110, 112, 111, 113, 40, 130, 99, 133, 121, 135, 126, 136,
    68, 146, 155, 156, 157, 159, 158, 160, 35, 143, 129, 168, 105, 169, 149, 170, 67, 145, 168, 179,
    151, 181, 180, 182, 63, 144, 144, 188, 140, 189, 189, 190, 69, 147, 172, 191, 164, 192, 193, 194,
    14, 58, 32, 59, 56, 60, 57, 61, 78, 115, 114, 116, 115, 117, 116, 118, 44, 131, 101, 134,
    122, 136, 127, 137, 81, 162, 161, 163, 164, 166, 165, 167, 58, 171, 131, 172, 115, 173, 162, 174,
    83, 173, 170, 183, 184, 186, 185, 187, 69, 172, 147, 191, 164, 193, 192, 194, 84, 174, 174, 195,
    196, 197, 197, 198,  1,  9, 11, 13,  5, 10, 12, 14,  5, 22, 29, 31, 27, 28, 30, 32,
    5, 24, 41, 47, 29, 35, 52, 58,  7, 25, 42, 48, 30, 36, 53, 59,  4, 22, 39, 45,
    22, 33, 45, 56,  6, 23, 40, 46, 28, 34, 51, 57,  6, 25, 43, 49, 31, 37, 54, 60,
    8, 26, 44, 50, 32, 38, 55, 61, 11, 41, 39, 43, 29, 42, 40, 44, 41, 96, 98, 100,
    95, 97, 99, 101, 29, 95, 98, 123, 128, 129, 130, 131, 42, 97, 119, 124, 129, 132, 133, 134,
    39, 98, 120, 121, 98, 119, 121, 122, 43, 100, 121, 125, 123, 124, 126, 127, 40, 99, 121, 126,
    130, 133, 135, 136, 44, 101, 122, 127, 131, 134, 136, 137,  9, 76, 41, 77, 41, 77, 66, 78,
    24, 92, 95, 102, 95, 102, 109, 114, 22, 92, 96, 103, 98, 105, 110, 115, 25, 93, 97, 104,
    99, 106, 111, 116, 22, 92, 98, 105, 96, 103, 110, 115, 25, 93, 99, 106, 97, 104, 111, 116,
    23, 93, 100, 107, 100, 107, 112, 117, 26, 94, 101, 108, 101, 108, 113, 118, 13, 77, 43, 79,
    52, 80, 68, 81, 47, 103, 123, 138, 143, 148, 155, 161, 31, 102, 100, 138, 130, 149, 146, 162,
    48, 104, 124, 139, 144, 150, 156, 163, 45, 105, 121, 140, 110, 151, 157, 164, 49, 107, 126, 141,
    145, 152, 158, 165, 46, 106, 125, 141, 146, 153, 159, 166, 50, 108, 127, 142, 147, 154, 160, 167,
    5, 41, 29, 52, 24, 47, 35, 58, 29, 98, 128, 130, 95, 123, 129, 131, 27, 95, 95, 143,
    95, 143, 143, 171, 30, 99, 129, 144, 109, 155, 168, 172, 22, 96, 98, 110, 92, 103, 105, 115,
    31, 100, 130, 146, 102, 138, 149, 162, 28, 97, 123, 145, 102, 148, 169, 173, 32, 101, 131, 147,
    114, 161, 170, 174, 12, 66, 40, 68, 35, 67, 63, 69, 52, 110, 130, 146, 143, 145, 144, 147,
    30, 109, 99, 155, 129, 168, 144, 172, 53, 111, 133, 156, 168, 179, 188, 191, 45, 110, 121, 157,
    105, 151, 140, 164, 54, 112, 135, 159, 169, 181, 189, 192, 51, 111, 126, 158, 149, 180, 189, 193,
    55, 113, 136, 160, 170, 182, 190, 194, 10, 77, 42, 80, 47, 82, 67, 83, 35, 105, 129, 149,
    143, 169, 168, 170, 28, 102, 97, 148, 123, 169, 145, 173, 36, 106, 132, 150, 155, 175, 179, 183,
    33, 103, 119, 151, 103, 176, 151, 184, 37, 107, 133, 153, 148, 177, 180, 185, 34, 104, 124, 152,
    138, 177, 181, 186, 38, 108, 134, 154, 161, 178, 182, 187, 14, 78, 44, 81, 58, 83, 69, 84,
    58, 115, 131, 162, 171, 173, 172, 174, 32, 114, 101, 161, 131, 170, 147, 174, 59, 116, 134, 163,
    172, 183, 191, 195, 56, 115, 122, 164, 115, 184, 164, 196, 60, 117, 136, 166, 173, 186, 193, 197,
    57, 116, 127, 165, 162, 185, 192, 197, 61, 118, 137, 167, 174, 187, 194, 198,  2, 10, 12, 17,
    6, 15, 16, 18, 10, 33, 35, 37, 28, 34, 36, 38, 12, 35, 66, 67, 40, 63, 68, 69,
    17, 37, 67, 70, 51, 64, 71, 72,  6, 28, 40, 51, 23, 34, 46, 57, 15, 34, 63, 64,
    34, 62, 64, 65, 16, 36, 68, 71, 46, 64, 73, 74, 18, 38, 69, 72, 57, 65, 74, 75,
    13, 47, 45, 49, 31, 48, 46, 50, 77, 103, 105, 107, 102, 104, 106, 108, 52, 143, 110, 145,
    130, 144, 146, 147, 80, 148, 151, 152, 149, 150, 153, 154, 43, 123, 121, 126, 100, 124, 125, 127,
    79, 138, 140, 141, 138, 139, 141, 142, 68, 155, 157, 158, 146, 156, 159, 160, 81, 161, 164, 165,
    162, 163, 166, 167, 13, 77, 52, 80, 43, 79, 68, 81, 47, 103, 143, 148, 123, 138, 155, 161,
    45, 105, 110, 151, 121, 140, 157, 164, 49, 107, 145, 152, 126, 141, 158, 165, 31, 102, 130, 149,
    100, 138, 146, 162, 48, 104, 144, 150, 124, 139, 156, 163, 46, 106, 146, 153, 125, 141, 159, 166,
    50, 108, 147, 154, 127, 142, 160, 167, 19, 82, 54, 85, 54, 85, 73, 86, 82, 176, 169, 177,
    169, 177, 175, 178, 54, 169, 112, 181, 135, 189, 159, 192, 85, 177, 181, 199, 189, 200, 201, 202,
    54, 169, 135, 189, 112, 181, 159, 192, 85, 177, 189, 200, 181, 199, 201, 202, 73, 175, 159, 201,
    159, 201, 203, 204, 86, 178, 192, 202, 192, 202, 204, 205,  7, 42, 30, 53, 25, 48, 36, 59,
    42, 119, 129, 133, 97, 124, 132, 134, 30, 129, 109, 168, 99, 144, 155, 172, 53, 133, 168, 188,
    111, 156, 179, 191, 25, 97, 99, 111, 93, 104, 106, 116, 48, 124, 144, 156, 104, 139, 150, 163,
    36, 132, 155, 179, 106, 150, 175, 183, 59, 134, 172, 191, 116, 163, 183, 195, 17, 67, 51, 71,
    37, 70, 64, 72, 80, 151, 149, 153, 148, 152, 150, 154, 53, 168, 111, 179, 133, 188, 156, 191,
    87, 180, 180, 206, 180, 206, 206, 207, 49, 145, 126, 158, 107, 152, 141, 165, 85, 181, 189, 201,
    177, 199, 200, 202, 71, 179, 158, 208, 153, 206, 201, 209, 88, 182, 193, 209, 185, 210, 211, 212,
    17, 80, 53, 87, 49, 85, 71, 88, 67, 151, 168, 180, 145, 181, 179, 182, 51, 149, 111, 180,
    126, 189, 158, 193, 71, 153, 179, 206, 158, 201, 208, 209, 37, 148, 133, 180, 107, 177, 153, 185,
    70, 152, 188, 206, 152, 199, 206, 210, 64, 150, 156, 206, 141, 200, 201, 211, 72, 154, 191, 207,
    165, 202, 209, 212, 20, 83, 55, 88, 60, 89, 74, 90, 83, 184, 170, 185, 173, 186, 183, 187,
    55, 170, 113, 182, 136, 190, 160, 194, 88, 185, 182, 210, 193, 211, 209, 212, 60, 173, 136, 193,
    117, 186, 166, 197, 89, 186, 190, 211, 186, 213, 211, 214, 74, 183, 160, 209, 166, 211, 204, 215,
    90, 187, 194, 212, 197, 214, 215, 216,  1, 11,  9, 13,  5, 12, 10, 14, 11, 39, 41, 43,
    29, 40, 42, 44,  9, 41, 76, 77, 41, 66, 77, 78, 13, 43, 77, 79, 52, 68, 80, 81,
    5, 29, 41, 52, 24, 35, 47, 58, 12, 40, 66, 68, 35, 63, 67, 69, 10, 42, 77, 80,
    47, 67, 82, 83, 14, 44, 78, 81, 58, 69, 83, 84,  5, 29, 22, 31, 27, 30, 28, 32,
    41, 98, 96, 100, 95, 99, 97, 101, 24, 95, 92, 102, 95, 109, 102, 114, 47, 123, 103, 138,
    143, 155, 148, 161, 29, 128, 98, 130, 95, 129, 123, 131, 52, 130, 110, 146, 143, 144, 145, 147,
    35, 129, 105, 149, 143, 168, 169, 170, 58, 131, 115, 162, 171, 172, 173, 174,  5, 41, 24, 47,
    29, 52, 35, 58, 29, 98, 95, 123, 128, 130, 129, 131, 22, 96, 92, 103, 98, 110, 105, 115,
    31, 100, 102, 138, 130, 146, 149, 162, 27, 95, 95, 143, 95, 143, 143, 171, 30, 99, 109, 155,
    129, 144, 168, 172, 28, 97, 102, 148, 123, 145, 169, 173, 32, 101, 114, 161, 131, 147, 170, 174,
    7, 42, 25, 48, 30, 53, 36, 59, 42, 119, 97, 124, 129, 133, 132, 134, 25, 97, 93, 104,
    99, 111, 106, 116, 48, 124, 104, 139, 144, 156, 150, 163, 30, 129, 99, 144, 109, 168, 155, 172,
    53, 133, 111, 156, 168, 188, 179, 191, 36, 132, 106, 150, 155, 179, 175, 183, 59, 134, 116, 163,
    172, 191, 183, 195,  4, 39, 22, 45, 22, 45, 33, 56, 39, 120, 98, 121, 98, 121, 119, 122,
    22, 98, 92, 105, 96, 110, 103, 115, 45, 121, 105, 140, 110, 157, 151, 164, 22, 98, 96, 110,
    92, 105, 103, 115, 45, 121, 110, 157, 105, 140, 151, 164, 33, 119, 103, 151, 103, 151, 176, 184,
    56, 122, 115, 164, 115, 164, 184, 196,  6, 40, 23, 46, 28, 51, 34, 57, 43, 121, 100, 125,
    123, 126, 124, 127, 25, 99, 93, 106, 97, 111, 104, 116, 49, 126, 107, 141, 145, 158, 152, 165,
    31, 130, 100, 146, 102, 149, 138, 162, 54, 135, 112, 159, 169, 189, 181, 192, 37, 133, 107, 153,
    148, 180, 177, 185, 60, 136, 117, 166, 173, 193, 186, 197,  6, 43, 25, 49, 31, 54, 37, 60,
    40, 121, 99, 126, 130, 135, 133, 136, 23, 100, 93, 107, 100, 112, 107, 117, 46, 125, 106, 141,
    146, 159, 153, 166, 28, 123, 97, 145, 102, 169, 148, 173, 51, 126, 111, 158, 149, 189, 180, 193,
    34, 124, 104, 152, 138, 181, 177, 186, 57, 127, 116, 165, 162, 192, 185, 197,  8, 44, 26, 50,
    32, 55, 38, 61, 44, 122, 101, 127, 131, 136, 134, 137, 26, 101, 94, 108, 101, 113, 108, 118,
    50, 127, 108, 142, 147, 160, 154, 167, 32, 131, 101, 147, 114, 170, 161, 174, 55, 136, 113, 160,
    170, 190, 182, 194, 38, 134, 108, 154, 161, 182, 178, 187, 61, 137, 118, 167, 174, 194, 187, 198,
    2, 12, 10, 17,  6, 16, 15, 18, 13, 45, 47, 49, 31, 46, 48, 50, 13, 52, 77, 80,
    43, 68, 79, 81, 19, 54, 82, 85, 54, 73, 85, 86,  7, 30, 42, 53, 25, 36, 48, 59,
    17, 51, 67, 71, 37, 64, 70, 72, 17, 53, 80, 87, 49, 71, 85, 88, 20, 55, 83, 88,
    60, 74, 89, 90, 10, 35, 33, 37, 28, 36, 34, 38, 77, 105, 103, 107, 102, 106, 104, 108,
    47, 143, 103, 148, 123, 155, 138, 161, 82, 169, 176, 177, 169, 175, 177, 178, 42, 129, 119, 133,
    97, 132, 124, 134, 80, 149, 151, 153, 148, 150, 152, 154, 67, 168, 151, 180, 145, 179, 181, 182,
    83, 170, 184, 185, 173, 183, 186, 187, 12, 66, 35, 67, 40, 68, 63, 69, 52, 110, 143, 145,
    130, 146, 144, 147, 45, 110, 105, 151, 121, 157, 140, 164, 54, 112, 169, 181, 135, 159, 189, 192,
    30, 109, 129, 168, 99, 155, 144, 172, 53, 111, 168, 179, 133, 156, 188, 191, 51, 111, 149, 180,
    126, 158, 189, 193, 55, 113, 170, 182, 136, 160, 190, 194, 17, 67, 37, 70, 51, 71, 64, 72,
    80, 151, 148, 152, 149, 153, 150, 154, 49, 145, 107, 152, 126, 158, 141, 165, 85, 181, 177, 199,
    189, 201, 200, 202, 53, 168, 133, 188, 111, 179, 156, 191, 87, 180, 180, 206, 180, 206, 206, 207,
    71, 179, 153, 206, 158, 208, 201, 209, 88, 182, 185, 210, 193, 209, 211, 212,  6, 40, 28, 51,
    23, 46, 34, 57, 43, 121, 123, 126, 100, 125, 124, 127, 31, 130, 102, 149, 100, 146, 138, 162,
    54, 135, 169, 189, 112, 159, 181, 192, 25, 99, 97, 111, 93, 106, 104, 116, 49, 126, 145, 158,
    107, 141, 152, 165, 37, 133, 148, 180, 107, 153, 177, 185, 60, 136, 173, 193, 117, 166, 186, 197,
    15, 63, 34, 64, 34, 64, 62, 65, 79, 140, 138, 141, 138, 141, 139, 142, 48, 144, 104, 150,
    124, 156, 139, 163, 85, 189, 177, 200, 181, 201, 199, 202, 48, 144, 124, 156, 104, 150, 139, 163,
    85, 189, 181, 201, 177, 200, 199, 202, 70, 188, 152, 206, 152, 206, 199, 210, 89, 190, 186, 211,
    186, 211, 213, 214, 16, 68, 36, 71, 46, 73, 64, 74, 68, 157, 155, 158, 146, 159, 156, 160,
    46, 146, 106, 153, 125, 159, 141, 166, 73, 159, 175, 201, 159, 203, 201, 204, 36, 155, 132, 179,
    106, 175, 150, 183, 71, 158, 179, 208, 153, 201, 206, 209, 64, 156, 150, 206, 141, 201, 200, 211,
    74, 160, 183, 209, 166, 204, 211, 215, 18, 69, 38, 72, 57, 74, 65, 75, 81, 164, 161, 165,
    162, 166, 163, 167, 50, 147, 108, 154, 127, 160, 142, 167, 86, 192, 178, 202, 192, 204, 202, 205,
    59, 172, 134, 191, 116, 183, 163, 195, 88, 193, 182, 209, 185, 211, 210, 212, 72, 191, 154, 207,
    165, 209, 202, 212, 90, 194, 187, 212, 197, 215, 214, 216,  2, 13, 13, 19,  7, 17, 17, 20,
    12, 45, 52, 54, 30, 51, 53, 55, 10, 47, 77, 82, 42, 67, 80, 83, 17, 49, 80, 85,
    53, 71, 87, 88,  6, 31, 43, 54, 25, 37, 49, 60, 16, 46, 68, 73, 36, 64, 71, 74,
    15, 48, 79, 85, 48, 70, 85, 89, 18, 50, 81, 86, 59, 72, 88, 90, 12, 52, 45, 54,
    30, 53, 51, 55, 66, 110, 110, 112, 109, 111, 111, 113, 35, 143, 105, 169, 129, 168, 149, 170,
    67, 145, 151, 181, 168, 179, 180, 182, 40, 130, 121, 135, 99, 133, 126, 136, 68, 146, 157, 159,
    155, 156, 158, 160, 63, 144, 140, 189, 144, 188, 189, 190, 69, 147, 164, 192, 172, 191, 193, 194,
    10, 77, 47, 82, 42, 80, 67, 83, 35, 105, 143, 169, 129, 149, 168, 170, 33, 103, 103, 176,
    119, 151, 151, 184, 37, 107, 148, 177, 133, 153, 180, 185, 28, 102, 123, 169, 97, 148, 145, 173,
    36, 106, 155, 175, 132, 150, 179, 183, 34, 104, 138, 177, 124, 152, 181, 186, 38, 108, 161, 178,
    134, 154, 182, 187, 17, 80, 49, 85, 53, 87, 71, 88, 67, 151, 145, 181, 168, 180, 179, 182,
    37, 148, 107, 177, 133, 180, 153, 185, 70, 152, 152, 199, 188, 206, 206, 210, 51, 149, 126, 189,
    111, 180, 158, 193, 71, 153, 158, 201, 179, 206, 208, 209, 64, 150, 141, 200, 156, 206, 201, 211,
    72, 154, 165, 202, 191, 207, 209, 212,  6, 43, 31, 54, 25, 49, 37, 60, 40, 121, 130, 135,
    99, 126, 133, 136, 28, 123, 102, 169, 97, 145, 148, 173, 51, 126, 149, 189, 111, 158, 180, 193,
    23, 100, 100, 112, 93, 107, 107, 117, 46, 125, 146, 159, 106, 141, 153, 166, 34, 124, 138, 181,
    104, 152, 177, 186, 57, 127, 162, 192, 116, 165, 185, 197, 16, 68, 46, 73, 36, 71, 64, 74,
    68, 157, 146, 159, 155, 158, 156, 160, 36, 155, 106, 175, 132, 179, 150, 183, 71, 158, 153, 201,
    179, 208, 206, 209, 46, 146, 125, 159, 106, 153, 141, 166, 73, 159, 159, 203, 175, 201, 201, 204,
    64, 156, 141, 201, 150, 206, 200, 211, 74, 160, 166, 204, 183, 209, 211, 215, 15, 79, 48, 85,
    48, 85, 70, 89, 63, 140, 144, 189, 144, 189, 188, 190, 34, 138, 104, 177, 124, 181, 152, 186,
    64, 141, 150, 200, 156, 201, 206, 211, 34, 138, 124, 181, 104, 177, 152, 186, 64, 141, 156, 201,
    150, 200, 206, 211, 62, 139, 139, 199, 139, 199, 199, 213, 65, 142, 163, 202, 163, 202, 210, 214,
    18, 81, 50, 86, 59, 88, 72, 90, 69, 164, 147, 192, 172, 193, 191, 194, 38, 161, 108, 178,
    134, 182, 154, 187, 72, 165, 154, 202, 191, 209, 207, 212, 57, 162, 127, 192, 116, 185, 165, 197,
    74, 166, 160, 204, 183, 211, 209, 215, 65, 163, 142, 202, 163, 210, 202, 214, 75, 167, 167, 205,
    195, 212, 212, 216,  3, 14, 14, 20,  8, 18, 18, 21, 14, 56, 58, 60, 32, 57, 59, 61,
    14, 58, 78, 83, 44, 69, 81, 84, 20, 60, 83, 89, 55, 74, 88, 90,  8, 32, 44, 55,
    26, 38, 50, 61, 18, 57, 69, 74, 38, 65, 72, 75, 18, 59, 81, 88, 50, 72, 86, 90,
    21, 61, 84, 90, 61, 75, 90, 91, 14, 58, 56, 60, 32, 59, 57, 61, 78, 115, 115, 117,
    114, 116, 116, 118, 58, 171, 115, 173, 131, 172, 162, 174, 83, 173, 184, 186, 170, 183, 185, 187,
    44, 131, 122, 136, 101, 134, 127, 137, 81, 162, 164, 166, 161, 163, 165, 167, 69, 172, 164, 193,
    147, 191, 192, 194, 84, 174, 196, 197, 174, 195, 197, 198, 14, 78, 58, 83, 44, 81, 69, 84,
    58, 115, 171, 173, 131, 162, 172, 174, 56, 115, 115, 184, 122, 164, 164, 196, 60, 117, 173, 186,
    136, 166, 193, 197, 32, 114, 131, 170, 101, 161, 147, 174, 59, 116, 172, 183, 134, 163, 191, 195,
    57, 116, 162, 185, 127, 165, 192, 197, 61, 118, 174, 187, 137, 167, 194, 198, 20, 83, 60, 89,
    55, 88, 74, 90, 83, 184, 173, 186, 170, 185, 183, 187, 60, 173, 117, 186, 136, 193, 166, 197,
    89, 186, 186, 213, 190, 211, 211, 214, 55, 170, 136, 190, 113, 182, 160, 194, 88, 185, 193, 211,
    182, 210, 209, 212, 74, 183, 166, 211, 160, 209, 204, 215, 90, 187, 197, 214, 194, 212, 215, 216,
    8, 44, 32, 55, 26, 50, 38, 61, 44, 122, 131, 136, 101, 127, 134, 137, 32, 131, 114, 170,
    101, 147, 161, 174, 55, 136, 170, 190, 113, 160, 182, 194, 26, 101, 101, 113, 94, 108, 108, 118,
    50, 127, 147, 160, 108, 142, 154, 167, 38, 134, 161, 182, 108, 154, 178, 187, 61, 137, 174, 194,
    118, 167, 187, 198, 18, 69, 57, 74, 38, 72, 65, 75, 81, 164, 162, 166, 161, 165, 163, 167,
    59, 172, 116, 183, 134, 191, 163, 195, 88, 193, 185, 211, 182, 209, 210, 212, 50, 147, 127, 160,
    108, 154, 142, 167, 86, 192, 192, 204, 178, 202, 202, 205, 72, 191, 165, 209, 154, 207, 202, 212,
    90, 194, 197, 215, 187, 212, 214, 216, 18, 81, 59, 88, 50, 86, 72, 90, 69, 164, 172, 193,
    147, 192, 191, 194, 57, 162, 116, 185, 127, 192, 165, 197, 74, 166, 183, 211, 160, 204, 209, 215,
    38, 161, 134, 182, 108, 178, 154, 187, 72, 165, 191, 209, 154, 202, 207, 212, 65, 163, 163, 210,
    142, 202, 202, 214, 75, 167, 195, 212, 167, 205, 212, 216, 21, 84, 61, 90, 61, 90, 75, 91,
    84, 196, 174, 197, 174, 197, 195, 198, 61, 174, 118, 187, 137, 194, 167, 198, 90, 197, 187, 214,
    194, 215, 212, 216, 61, 174, 137, 194, 118, 187, 167, 198, 90, 197, 194, 215, 187, 214, 212, 216,
    75, 195, 167, 212, 167, 212, 205, 216, 91, 198, 198, 216, 198, 216, 216, 217
};

const unsigned int igraph_i_isographs_3[] =  { 0, 1, 3, 5, 6, 7, 10, 11, 15, 21,
                                               23, 25, 27, 30, 31, 63
                                             };
const unsigned int igraph_i_isographs_3u[] = { 0, 1, 3, 7 };
const unsigned int igraph_i_isographs_4[] = {
    0,    1,    3,    7,    9,   10,   11,   14,   15,   18,   19,   20,   21,
    22,   23,   27,   29,   30,   31,   54,   55,   63,   73,   75,   76,   77,
    79,   81,   83,   84,   85,   86,   87,   90,   91,   92,   93,   94,   95,
    98,   99,  100,  101,  102,  103,  106,  107,  108,  109,  110,  111,  115,
    116,  117,  118,  119,  122,  123,  124,  125,  126,  127,  219,  220,  221,
    223,  228,  229,  230,  231,  237,  238,  239,  246,  247,  255,  292,  293,
    295,  301,  302,  303,  310,  311,  319,  365,  367,  373,  375,  382,  383,
    511,  585,  587,  591,  593,  594,  595,  596,  597,  598,  599,  601,  602,
    603,  604,  605,  606,  607,  625,  626,  627,  630,  631,  633,  634,  635,
    638,  639,  659,  660,  661,  663,  666,  667,  669,  670,  671,  674,  675,
    678,  679,  683,  686,  687,  694,  695,  703,  729,  731,  732,  733,  735,
    737,  739,  741,  742,  743,  745,  746,  747,  748,  749,  750,  751,  753,
    755,  756,  757,  758,  759,  761,  762,  763,  764,  765,  766,  767,  819,
    822,  823,  826,  827,  830,  831,  875,  876,  877,  879,  883,  885,  886,
    887,  891,  892,  893,  894,  895,  947,  949,  951,  955,  957,  958,  959,
    1019, 1020, 1021, 1023, 1755, 1757, 1758, 1759, 1782, 1783, 1791, 1883, 1887,
    1907, 1911, 1917, 1918, 1919, 2029, 2031, 2039, 2047, 4095
};
const unsigned int igraph_i_isographs_4u[] = { 0, 1, 3, 7, 11, 12, 13,
                                               15, 30, 31, 63
                                             };

const unsigned int igraph_i_classedges_3[] = { 1, 2, 0, 2, 2, 1, 0, 1, 2, 0, 1, 0 };
const unsigned int igraph_i_classedges_3u[] = { 1, 2, 0, 2, 0, 1 };
const unsigned int igraph_i_classedges_4[] = { 2, 3, 1, 3, 0, 3, 3, 2, 1, 2, 0, 2,
                                               3, 1, 2, 1, 0, 1, 3, 0, 2, 0, 1, 0
                                             };
const unsigned int igraph_i_classedges_4u[] = { 2, 3, 1, 3, 0, 3, 1, 2, 0, 2, 0, 1 };

/**
 * \section about_graph_isomorphism
 *
 * <para>igraph provides four set of functions to deal with graph
 * isomorphism problems.</para>
 *
 * <para>The \ref igraph_isomorphic() and \ref igraph_subisomorphic()
 * functions make up the first set (in addition with the \ref
 * igraph_permute_vertices() function). These functions choose the
 * algorithm which is best for the supplied input graph. (The choice is
 * not very sophisticated though, see their documentation for
 * details.)</para>
 *
 * <para>The VF2 graph (and subgraph) isomorphism algorithm is implemented in
 * igraph, these functions are the second set. See \ref
 * igraph_isomorphic_vf2() and \ref igraph_subisomorphic_vf2() for
 * starters.</para>
 *
 * <para>Functions for the BLISS algorithm constitute the third set,
 * see \ref igraph_isomorphic_bliss().</para>
 *
 * <para>Finally, the isomorphism classes of all graphs with three and
 * four vertices are precomputed and stored in igraph, so for these
 * small graphs there is a very simple fast way to decide isomorphism.
 * See \ref igraph_isomorphic_34().
 * </para>
 */

/**
 * \function igraph_isoclass
 * \brief Determine the isomorphism class of a graph with 3 or 4 vertices
 *
 * </para><para>
 * All graphs with a given number of vertices belong to a number of
 * isomorphism classes, with every graph in a given class being
 * isomorphic to each other.
 *
 * </para><para>
 * This function gives the isomorphism class (a number) of a
 * graph. Two graphs have the same isomorphism class if and only if
 * they are isomorphic.
 *
 * </para><para>
 * The first isomorphism class is numbered zero and it is the empty
 * graph, the last isomorphism class is the full graph. The number of
 * isomorphism class for directed graphs with three vertices is 16
 * (between 0 and 15), for undirected graph it is only 4. For graphs
 * with four vertices it is 218 (directed) and 11 (undirected).
 *
 * </para><para>
 * Multi-edges and self-loops are ignored by this function.
 *
 * \param graph The graph object.
 * \param isoclass Pointer to an integer, the isomorphism class will
 *        be stored here.
 * \return Error code.
 * \sa \ref igraph_isomorphic(), \ref igraph_isoclass_subgraph(),
 * \ref igraph_isoclass_create(), \ref igraph_motifs_randesu().
 *
 * Because of some limitations this function works only for graphs
 * with three of four vertices.
 *
 * </para><para>
 * Time complexity: O(|E|), the number of edges in the graph.
 */

int igraph_isoclass(const igraph_t *graph, igraph_integer_t *isoclass) {
    long int e;
    long int no_of_nodes = igraph_vcount(graph);
    long int no_of_edges = igraph_ecount(graph);
    igraph_integer_t from, to;
    unsigned char idx, mul;
    const unsigned int *arr_idx, *arr_code;
    int code = 0;

    if (no_of_nodes < 3 || no_of_nodes > 4) {
        IGRAPH_ERROR("Only implemented for graphs with 3 or 4 vertices",
                     IGRAPH_UNIMPLEMENTED);
    }

    if (igraph_is_directed(graph)) {
        if (no_of_nodes == 3) {
            arr_idx = igraph_i_isoclass_3_idx;
            arr_code = igraph_i_isoclass2_3;
            mul = 3;
        } else {
            arr_idx = igraph_i_isoclass_4_idx;
            arr_code = igraph_i_isoclass2_4;
            mul = 4;
        }
    } else {
        if (no_of_nodes == 3) {
            arr_idx = igraph_i_isoclass_3u_idx;
            arr_code = igraph_i_isoclass2_3u;
            mul = 3;
        } else {
            arr_idx = igraph_i_isoclass_4u_idx;
            arr_code = igraph_i_isoclass2_4u;
            mul = 4;
        }
    }

    for (e = 0; e < no_of_edges; e++) {
        igraph_edge(graph, (igraph_integer_t) e, &from, &to);
        idx = (unsigned char) (mul * from + to);
        code |= arr_idx[idx];
    }

    *isoclass = (igraph_integer_t) arr_code[code];
    return 0;
}

/**
 * \function igraph_isomorphic
 * \brief Decides whether two graphs are isomorphic
 *
 * </para><para>
 * In simple terms, two graphs are isomorphic if they become indistinguishable
 * from each other once their vertex labels are removed (rendering the vertices
 * within each graph indistiguishable). More precisely, two graphs are isomorphic
 * if there is a one-to-one mapping from the vertices of the first one
 * to the vertices of the second such that it transforms the edge set of the
 * first graph into the edge set of the second. This mapping is called
 * an \em isomorphism.
 *
 * </para><para>Currently, this function supports simple graphs and graphs
 * with self-loops, but does not support multigraphs.
 *
 * </para><para>This function decides which graph isomorphism algorithm to be
 * used based on the input graphs. Right now it does the following:
 * \olist
 * \oli If one graph is directed and the other undirected then an
 *    error is triggered.
 * \oli If one of the graphs has multi-edges then an error is triggered.
 * \oli If the two graphs does not have the same number of vertices
 *    and edges it returns with \c FALSE.
 * \oli Otherwise, if the graphs have three or four vertices then an O(1)
 *    algorithm is used with precomputed data.
 * \oli Otherwise BLISS is used, see \ref igraph_isomorphic_bliss().
 * \endolist
 *
 * </para><para>Please call the VF2 and BLISS functions directly if you need
 * something more sophisticated, e.g. you need the isomorphic mapping.
 *
 * \param graph1 The first graph.
 * \param graph2 The second graph.
 * \param iso Pointer to a logical variable, will be set to TRUE (1)
 *        if the two graphs are isomorphic, and FALSE (0) otherwise.
 * \return Error code.
 * \sa \ref igraph_isoclass(), \ref igraph_isoclass_subgraph(),
 * \ref igraph_isoclass_create().
 *
 * Time complexity: exponential.
 */

int igraph_isomorphic(const igraph_t *graph1, const igraph_t *graph2,
                      igraph_bool_t *iso) {

    long int nodes1 = igraph_vcount(graph1), nodes2 = igraph_vcount(graph2);
    long int edges1 = igraph_ecount(graph1), edges2 = igraph_ecount(graph2);
    igraph_bool_t dir1 = igraph_is_directed(graph1), dir2 = igraph_is_directed(graph2);
    igraph_bool_t loop1, loop2, multi1, multi2;

    IGRAPH_CHECK(igraph_has_multiple(graph1, &multi1));
    IGRAPH_CHECK(igraph_has_multiple(graph2, &multi2));

    if (multi1 || multi2) {
        IGRAPH_ERROR("Isomorphism testing is not implemented for multigraphs", IGRAPH_UNIMPLEMENTED);
    }

    if (dir1 != dir2) {
        IGRAPH_ERROR("Cannot compare directed and undirected graphs", IGRAPH_EINVAL);
    } else if (nodes1 != nodes2 || edges1 != edges2) {
        *iso = 0;
    } else if (nodes1 == 3 || nodes1 == 4) {
        IGRAPH_CHECK(igraph_has_loop(graph1, &loop1));
        IGRAPH_CHECK(igraph_has_loop(graph2, &loop2));
        if (!loop1 && !loop2) {
            IGRAPH_CHECK(igraph_isomorphic_34(graph1, graph2, iso));
        } else {
            IGRAPH_CHECK(igraph_isomorphic_bliss(graph1, graph2, NULL, NULL, iso,
                                                 0, 0, /*sh=*/ IGRAPH_BLISS_F, 0, 0));
        }
    } else {
        IGRAPH_CHECK(igraph_isomorphic_bliss(graph1, graph2, NULL, NULL, iso,
                                             0, 0, /*sh=*/ IGRAPH_BLISS_F, 0, 0));
    }

    return 0;
}

/**
 * \function igraph_isomorphic_34
 * Graph isomorphism for 3-4 vertices
 *
 * This function uses precomputed indices to decide isomorphism
 * problems for graphs with only 3 or 4 vertices. Multi-edges
 * and self-loops are ignored by this function.
 * \param graph1 The first input graph.
 * \param graph2 The second input graph. Must have the same
 *   directedness as \p graph1.
 * \param iso Pointer to a boolean, the result is stored here.
 * \return Error code.
 *
 * Time complexity: O(1).
 */

int igraph_isomorphic_34(const igraph_t *graph1, const igraph_t *graph2,
                         igraph_bool_t *iso) {

    igraph_integer_t class1, class2;
    IGRAPH_CHECK(igraph_isoclass(graph1, &class1));
    IGRAPH_CHECK(igraph_isoclass(graph2, &class2));
    *iso = (class1 == class2);
    return 0;
}

/**
 * \function igraph_isoclass_subgraph
 * \brief The isomorphism class of a subgraph of a graph.
 *
 * </para><para>
 * This function is only implemented for subgraphs with three or four
 * vertices.
 * \param graph The graph object.
 * \param vids A vector containing the vertex ids to be considered as
 *        a subgraph. Each vertex id should be included at most once.
 * \param isoclass Pointer to an integer, this will be set to the
 *        isomorphism class.
 * \return Error code.
 * \sa \ref igraph_isoclass(), \ref igraph_isomorphic(),
 * \ref igraph_isoclass_create().
 *
 * Time complexity: O((d+n)*n), d is the average degree in the network,
 * and n is the number of vertices in \c vids.
 */

int igraph_isoclass_subgraph(const igraph_t *graph, igraph_vector_t *vids,
                             igraph_integer_t *isoclass) {
    int nodes = (int) igraph_vector_size(vids);
    igraph_bool_t directed = igraph_is_directed(graph);
    igraph_vector_t neis;

    unsigned char mul, idx;
    const unsigned int *arr_idx, *arr_code;
    int code = 0;

    long int i, j, s;

    if (nodes < 3 || nodes > 4) {
        IGRAPH_ERROR("Only for three- or four-vertex subgraphs",
                     IGRAPH_UNIMPLEMENTED);
    }

    IGRAPH_VECTOR_INIT_FINALLY(&neis, 0);

    if (directed) {
        if (nodes == 3) {
            arr_idx = igraph_i_isoclass_3_idx;
            arr_code = igraph_i_isoclass2_3;
            mul = 3;
        } else {
            arr_idx = igraph_i_isoclass_4_idx;
            arr_code = igraph_i_isoclass2_4;
            mul = 4;
        }
    } else {
        if (nodes == 3) {
            arr_idx = igraph_i_isoclass_3u_idx;
            arr_code = igraph_i_isoclass2_3u;
            mul = 3;
        } else {
            arr_idx = igraph_i_isoclass_4u_idx;
            arr_code = igraph_i_isoclass2_4u;
            mul = 4;
        }
    }

    for (i = 0; i < nodes; i++) {
        long int from = (long int) VECTOR(*vids)[i];
        igraph_neighbors(graph, &neis, (igraph_integer_t) from, IGRAPH_OUT);
        s = igraph_vector_size(&neis);
        for (j = 0; j < s; j++) {
            long int nei = (long int) VECTOR(neis)[j], to;
            if (igraph_vector_search(vids, 0, nei, &to)) {
                idx = (unsigned char) (mul * i + to);
                code |= arr_idx[idx];
            }
        }
    }

    *isoclass = (igraph_integer_t) arr_code[code];
    igraph_vector_destroy(&neis);
    IGRAPH_FINALLY_CLEAN(1);
    return 0;
}

/**
 * \function igraph_isoclass_create
 * \brief Creates a graph from the given isomorphism class.
 *
 * </para><para>
 * This function is implemented only for graphs with three or four
 * vertices.
 * \param graph Pointer to an uninitialized graph object.
 * \param size The number of vertices to add to the graph.
 * \param number The isomorphism class.
 * \param directed Logical constant, whether to create a directed
 *        graph.
 * \return Error code.
 * \sa \ref igraph_isoclass(),
 * \ref igraph_isoclass_subgraph(),
 * \ref igraph_isomorphic().
 *
 * Time complexity: O(|V|+|E|), the number of vertices plus the number
 * of edges in the graph to create.
 */

int igraph_isoclass_create(igraph_t *graph, igraph_integer_t size,
                           igraph_integer_t number, igraph_bool_t directed) {
    igraph_vector_t edges;
    const unsigned int *classedges;
    long int power;
    long int code;
    long int pos;

    if (size < 3 || size > 4) {
        IGRAPH_ERROR("Only for graphs with three of four vertices",
                     IGRAPH_UNIMPLEMENTED);
    }

    IGRAPH_VECTOR_INIT_FINALLY(&edges, 0);

    if (directed) {
        if (size == 3) {
            classedges = igraph_i_classedges_3;

            if (number < 0 ||
                number >= (int)(sizeof(igraph_i_isographs_3) / sizeof(unsigned int))) {
                IGRAPH_ERROR("`number' invalid, cannot create graph", IGRAPH_EINVAL);
            }

            code = igraph_i_isographs_3[ (long int) number];
            power = 32;
        } else {
            classedges = igraph_i_classedges_4;

            if (number < 0 ||
                number >= (int)(sizeof(igraph_i_isographs_4) / sizeof(unsigned int))) {
                IGRAPH_ERROR("`number' invalid, cannot create graph", IGRAPH_EINVAL);
            }

            code = igraph_i_isographs_4[ (long int) number];
            power = 2048;
        }
    } else {
        if (size == 3) {
            classedges = igraph_i_classedges_3u;

            if (number < 0 ||
                number >= (int)(sizeof(igraph_i_isographs_3u) /
                                sizeof(unsigned int))) {
                IGRAPH_ERROR("`number' invalid, cannot create graph", IGRAPH_EINVAL);
            }

            code = igraph_i_isographs_3u[ (long int) number];
            power = 4;
        } else {
            classedges = igraph_i_classedges_4u;

            if (number < 0 ||
                number >= (int)(sizeof(igraph_i_isographs_4u) /
                                sizeof(unsigned int))) {
                IGRAPH_ERROR("`number' invalid, cannot create graph", IGRAPH_EINVAL);
            }

            code = igraph_i_isographs_4u[ (long int) number];
            power = 32;
        }
    }

    pos = 0;
    while (code > 0) {
        if (code >= power) {
            IGRAPH_CHECK(igraph_vector_push_back(&edges, classedges[2 * pos]));
            IGRAPH_CHECK(igraph_vector_push_back(&edges, classedges[2 * pos + 1]));
            code -= power;
        }
        power /= 2;
        pos++;
    }

    IGRAPH_CHECK(igraph_create(graph, &edges, size, directed));
    igraph_vector_destroy(&edges);
    IGRAPH_FINALLY_CLEAN(1);
    return 0;
}

/**
 * \section about_vf2
 *
 * <para>
 * The VF2 algorithm can search for a subgraph in a larger graph, or check if two
 * graphs are isomorphic. See P. Foggia, C. Sansone, M. Vento, An Improved algorithm for
 * matching large graphs, Proc. of the 3rd IAPR-TC-15 International
 * Workshop on Graph-based Representations, Italy, 2001.
 * </para>
 *
 * <para>
 * VF2 supports both vertex and edge-colored graphs, as well as custom vertex or edge
 * compatibility functions.
 * </para>
 *
 * <para>
 * VF2 works with both directed and undirected graphs. Only simple graphs are supported.
 * Self-loops or multi-edges must not be present in the graphs. Currently, the VF2
 * functions do not check that the input graph is simple: it is the responsibility
 * of the user to pass in valid input.
 * </para>
 */

/**
 * \function igraph_isomorphic_function_vf2
 * The generic VF2 interface
 *
 * </para><para>
 * This function is an implementation of the VF2 isomorphism algorithm,
 * see P. Foggia, C. Sansone, M. Vento, An Improved algorithm for
 * matching large graphs, Proc. of the 3rd IAPR-TC-15 International
 * Workshop on Graph-based Representations, Italy, 2001.</para>
 *
 * <para>For using it you need to define a callback function of type
 * \ref igraph_isohandler_t. This function will be called whenever VF2
 * finds an isomorphism between the two graphs. The mapping between
 * the two graphs will be also provided to this function. If the
 * callback returns a nonzero value then the search is continued,
 * otherwise it stops. The callback function must not destroy the
 * mapping vectors that are passed to it.
 * \param graph1 The first input graph.
 * \param graph2 The second input graph.
 * \param vertex_color1 An optional color vector for the first graph. If
 *   color vectors are given for both graphs, then the isomorphism is
 *   calculated on the colored graphs; i.e. two vertices can match
 *   only if their color also matches. Supply a null pointer here if
 *   your graphs are not colored.
 * \param vertex_color2 An optional color vector for the second graph. See
 *   the previous argument for explanation.
 * \param edge_color1 An optional edge color vector for the first
 *   graph. The matching edges in the two graphs must have matching
 *   colors as well. Supply a null pointer here if your graphs are not
 *   edge-colored.
 * \param edge_color2 The edge color vector for the second graph.
 * \param map12 Pointer to an initialized vector or \c NULL. If not \c
 *   NULL and the supplied graphs are isomorphic then the permutation
 *   taking \p graph1 to \p graph is stored here. If not \c NULL and the
 *   graphs are not isomorphic then a zero-length vector is returned.
 * \param map21 This is the same as \p map12, but for the permutation
 *   taking \p graph2 to \p graph1.
 * \param isohandler_fn The callback function to be called if an
 *   isomorphism is found. See also \ref igraph_isohandler_t.
 * \param node_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two nodes are compatible.
 * \param edge_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two edges are compatible.
 * \param arg Extra argument to supply to functions \p isohandler_fn, \p
 *   node_compat_fn and \p edge_compat_fn.
 * \return Error code.
 *
 * Time complexity: exponential.
 */

int igraph_isomorphic_function_vf2(const igraph_t *graph1, const igraph_t *graph2,
                                   const igraph_vector_int_t *vertex_color1,
                                   const igraph_vector_int_t *vertex_color2,
                                   const igraph_vector_int_t *edge_color1,
                                   const igraph_vector_int_t *edge_color2,
                                   igraph_vector_t *map12,
                                   igraph_vector_t *map21,
                                   igraph_isohandler_t *isohandler_fn,
                                   igraph_isocompat_t *node_compat_fn,
                                   igraph_isocompat_t *edge_compat_fn,
                                   void *arg) {

    long int no_of_nodes = igraph_vcount(graph1);
    long int no_of_edges = igraph_ecount(graph1);
    igraph_vector_t mycore_1, mycore_2, *core_1 = &mycore_1, *core_2 = &mycore_2;
    igraph_vector_t in_1, in_2, out_1, out_2;
    long int in_1_size = 0, in_2_size = 0, out_1_size = 0, out_2_size = 0;
    igraph_vector_t *inneis_1, *inneis_2, *outneis_1, *outneis_2;
    long int matched_nodes = 0;
    long int depth;
    long int cand1, cand2;
    long int last1, last2;
    igraph_stack_t path;
    igraph_lazy_adjlist_t inadj1, inadj2, outadj1, outadj2;
    igraph_vector_t indeg1, indeg2, outdeg1, outdeg2;

    if (igraph_is_directed(graph1) != igraph_is_directed(graph2)) {
        IGRAPH_ERROR("Cannot compare directed and undirected graphs",
                     IGRAPH_EINVAL);
    }

    if ( (vertex_color1 && !vertex_color2) || (!vertex_color1 && vertex_color2) ) {
        IGRAPH_WARNING("Only one graph is vertex-colored, vertex colors will be ignored");
        vertex_color1 = vertex_color2 = 0;
    }

    if ( (edge_color1 && !edge_color2) || (!edge_color1 && edge_color2)) {
        IGRAPH_WARNING("Only one graph is edge-colored, edge colors will be ignored");
        edge_color1 = edge_color2 = 0;
    }

    if (no_of_nodes != igraph_vcount(graph2) ||
        no_of_edges != igraph_ecount(graph2)) {
        return 0;
    }

    if (vertex_color1) {
        if (igraph_vector_int_size(vertex_color1) != no_of_nodes ||
            igraph_vector_int_size(vertex_color2) != no_of_nodes) {
            IGRAPH_ERROR("Invalid vertex color vector length", IGRAPH_EINVAL);
        }
    }

    if (edge_color1) {
        if (igraph_vector_int_size(edge_color1) != no_of_edges ||
            igraph_vector_int_size(edge_color2) != no_of_edges) {
            IGRAPH_ERROR("Invalid edge color vector length", IGRAPH_EINVAL);
        }
    }

    /* Check color distribution */
    if (vertex_color1) {
        int ret = 0;
        igraph_vector_int_t tmp1, tmp2;
        IGRAPH_CHECK(igraph_vector_int_copy(&tmp1, vertex_color1));
        IGRAPH_FINALLY(igraph_vector_int_destroy, &tmp1);
        IGRAPH_CHECK(igraph_vector_int_copy(&tmp2, vertex_color2));
        IGRAPH_FINALLY(igraph_vector_int_destroy, &tmp2);
        igraph_vector_int_sort(&tmp1);
        igraph_vector_int_sort(&tmp2);
        ret = !igraph_vector_int_all_e(&tmp1, &tmp2);
        igraph_vector_int_destroy(&tmp1);
        igraph_vector_int_destroy(&tmp2);
        IGRAPH_FINALLY_CLEAN(2);
        if (ret) {
            return 0;
        }
    }

    /* Check edge color distribution */
    if (edge_color1) {
        int ret = 0;
        igraph_vector_int_t tmp1, tmp2;
        IGRAPH_CHECK(igraph_vector_int_copy(&tmp1, edge_color1));
        IGRAPH_FINALLY(igraph_vector_int_destroy, &tmp1);
        IGRAPH_CHECK(igraph_vector_int_copy(&tmp2, edge_color2));
        IGRAPH_FINALLY(igraph_vector_int_destroy, &tmp2);
        igraph_vector_int_sort(&tmp1);
        igraph_vector_int_sort(&tmp2);
        ret = !igraph_vector_int_all_e(&tmp1, &tmp2);
        igraph_vector_int_destroy(&tmp1);
        igraph_vector_int_destroy(&tmp2);
        IGRAPH_FINALLY_CLEAN(2);
        if (ret) {
            return 0;
        }
    }

    if (map12) {
        core_1 = map12;
        IGRAPH_CHECK(igraph_vector_resize(core_1, no_of_nodes));
    } else {
        IGRAPH_VECTOR_INIT_FINALLY(core_1, no_of_nodes);
    }
    igraph_vector_fill(core_1, -1);
    if (map21) {
        core_2 = map21;
        IGRAPH_CHECK(igraph_vector_resize(core_2, no_of_nodes));
        igraph_vector_null(core_2);
    } else {
        IGRAPH_VECTOR_INIT_FINALLY(core_2, no_of_nodes);
    }
    igraph_vector_fill(core_2, -1);

    IGRAPH_VECTOR_INIT_FINALLY(&in_1, no_of_nodes);
    IGRAPH_VECTOR_INIT_FINALLY(&in_2, no_of_nodes);
    IGRAPH_VECTOR_INIT_FINALLY(&out_1, no_of_nodes);
    IGRAPH_VECTOR_INIT_FINALLY(&out_2, no_of_nodes);
    IGRAPH_CHECK(igraph_stack_init(&path, 0));
    IGRAPH_FINALLY(igraph_stack_destroy, &path);
    IGRAPH_CHECK(igraph_lazy_adjlist_init(graph1, &inadj1, IGRAPH_IN,
                                          IGRAPH_SIMPLIFY));
    IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &inadj1);
    IGRAPH_CHECK(igraph_lazy_adjlist_init(graph1, &outadj1, IGRAPH_OUT,
                                          IGRAPH_SIMPLIFY));
    IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &outadj1);
    IGRAPH_CHECK(igraph_lazy_adjlist_init(graph2, &inadj2, IGRAPH_IN,
                                          IGRAPH_SIMPLIFY));
    IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &inadj2);
    IGRAPH_CHECK(igraph_lazy_adjlist_init(graph2, &outadj2, IGRAPH_OUT,
                                          IGRAPH_SIMPLIFY));
    IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &outadj2);
    IGRAPH_VECTOR_INIT_FINALLY(&indeg1, 0);
    IGRAPH_VECTOR_INIT_FINALLY(&indeg2, 0);
    IGRAPH_VECTOR_INIT_FINALLY(&outdeg1, 0);
    IGRAPH_VECTOR_INIT_FINALLY(&outdeg2, 0);

    IGRAPH_CHECK(igraph_stack_reserve(&path, no_of_nodes * 2));
    IGRAPH_CHECK(igraph_degree(graph1, &indeg1, igraph_vss_all(),
                               IGRAPH_IN, IGRAPH_LOOPS));
    IGRAPH_CHECK(igraph_degree(graph2, &indeg2, igraph_vss_all(),
                               IGRAPH_IN, IGRAPH_LOOPS));
    IGRAPH_CHECK(igraph_degree(graph1, &outdeg1, igraph_vss_all(),
                               IGRAPH_OUT, IGRAPH_LOOPS));
    IGRAPH_CHECK(igraph_degree(graph2, &outdeg2, igraph_vss_all(),
                               IGRAPH_OUT, IGRAPH_LOOPS));

    depth = 0; last1 = -1; last2 = -1;
    while (depth >= 0) {
        long int i;

        IGRAPH_ALLOW_INTERRUPTION();

        cand1 = -1; cand2 = -1;
        /* Search for the next pair to try */
        if ((in_1_size != in_2_size) ||
            (out_1_size != out_2_size)) {
            /* step back, nothing to do */
        } else if (out_1_size > 0 && out_2_size > 0) {
            /**************************************************************/
            /* cand2, search not always needed */
            if (last2 >= 0) {
                cand2 = last2;
            } else {
                i = 0;
                while (cand2 < 0 && i < no_of_nodes) {
                    if (VECTOR(out_2)[i] > 0 && VECTOR(*core_2)[i] < 0) {
                        cand2 = i;
                    }
                    i++;
                }
            }
            /* search for cand1 now, it should be bigger than last1 */
            i = last1 + 1;
            while (cand1 < 0 && i < no_of_nodes) {
                if (VECTOR(out_1)[i] > 0 && VECTOR(*core_1)[i] < 0) {
                    cand1 = i;
                }
                i++;
            }
        } else if (in_1_size > 0 && in_2_size > 0) {
            /**************************************************************/
            /* cand2, search not always needed */
            if (last2 >= 0) {
                cand2 = last2;
            } else {
                i = 0;
                while (cand2 < 0 && i < no_of_nodes) {
                    if (VECTOR(in_2)[i] > 0 && VECTOR(*core_2)[i] < 0) {
                        cand2 = i;
                    }
                    i++;
                }
            }
            /* search for cand1 now, should be bigger than last1 */
            i = last1 + 1;
            while (cand1 < 0 && i < no_of_nodes) {
                if (VECTOR(in_1)[i] > 0 && VECTOR(*core_1)[i] < 0) {
                    cand1 = i;
                }
                i++;
            }
        } else {
            /**************************************************************/
            /* cand2, search not always needed */
            if (last2 >= 0) {
                cand2 = last2;
            } else {
                i = 0;
                while (cand2 < 0 && i < no_of_nodes) {
                    if (VECTOR(*core_2)[i] < 0) {
                        cand2 = i;
                    }
                    i++;
                }
            }
            /* search for cand1, should be bigger than last1 */
            i = last1 + 1;
            while (cand1 < 0 && i < no_of_nodes) {
                if (VECTOR(*core_1)[i] < 0) {
                    cand1 = i;
                }
                i++;
            }
        }

        /* Ok, we have cand1, cand2 as candidates. Or not? */
        if (cand1 < 0 || cand2 < 0) {
            /**************************************************************/
            /* dead end, step back, if possible. Otherwise we'll terminate */
            if (depth >= 1) {
                last2 = (long int) igraph_stack_pop(&path);
                last1 = (long int) igraph_stack_pop(&path);
                matched_nodes -= 1;
                VECTOR(*core_1)[last1] = -1;
                VECTOR(*core_2)[last2] = -1;

                if (VECTOR(in_1)[last1] != 0) {
                    in_1_size += 1;
                }
                if (VECTOR(out_1)[last1] != 0) {
                    out_1_size += 1;
                }
                if (VECTOR(in_2)[last2] != 0) {
                    in_2_size += 1;
                }
                if (VECTOR(out_2)[last2] != 0) {
                    out_2_size += 1;
                }

                inneis_1 = igraph_lazy_adjlist_get(&inadj1, (igraph_integer_t) last1);
                for (i = 0; i < igraph_vector_size(inneis_1); i++) {
                    long int node = (long int) VECTOR(*inneis_1)[i];
                    if (VECTOR(in_1)[node] == depth) {
                        VECTOR(in_1)[node] = 0;
                        in_1_size -= 1;
                    }
                }
                outneis_1 = igraph_lazy_adjlist_get(&outadj1, (igraph_integer_t) last1);
                for (i = 0; i < igraph_vector_size(outneis_1); i++) {
                    long int node = (long int) VECTOR(*outneis_1)[i];
                    if (VECTOR(out_1)[node] == depth) {
                        VECTOR(out_1)[node] = 0;
                        out_1_size -= 1;
                    }
                }
                inneis_2 = igraph_lazy_adjlist_get(&inadj2, (igraph_integer_t) last2);
                for (i = 0; i < igraph_vector_size(inneis_2); i++) {
                    long int node = (long int) VECTOR(*inneis_2)[i];
                    if (VECTOR(in_2)[node] == depth) {
                        VECTOR(in_2)[node] = 0;
                        in_2_size -= 1;
                    }
                }
                outneis_2 = igraph_lazy_adjlist_get(&outadj2, (igraph_integer_t) last2);
                for (i = 0; i < igraph_vector_size(outneis_2); i++) {
                    long int node = (long int) VECTOR(*outneis_2)[i];
                    if (VECTOR(out_2)[node] == depth) {
                        VECTOR(out_2)[node] = 0;
                        out_2_size -= 1;
                    }
                }

            } /* end of stepping back */

            depth -= 1;

        } else {
            /**************************************************************/
            /* step forward if worth, check if worth first */
            long int xin1 = 0, xin2 = 0, xout1 = 0, xout2 = 0;
            igraph_bool_t end = 0;
            inneis_1 = igraph_lazy_adjlist_get(&inadj1, (igraph_integer_t) cand1);
            outneis_1 = igraph_lazy_adjlist_get(&outadj1, (igraph_integer_t) cand1);
            inneis_2 = igraph_lazy_adjlist_get(&inadj2, (igraph_integer_t) cand2);
            outneis_2 = igraph_lazy_adjlist_get(&outadj2, (igraph_integer_t) cand2);
            if (VECTOR(indeg1)[cand1] != VECTOR(indeg2)[cand2] ||
                VECTOR(outdeg1)[cand1] != VECTOR(outdeg2)[cand2]) {
                end = 1;
            }
            if (vertex_color1 && VECTOR(*vertex_color1)[cand1] != VECTOR(*vertex_color2)[cand2]) {
                end = 1;
            }
            if (node_compat_fn && !node_compat_fn(graph1, graph2,
                                                  (igraph_integer_t) cand1,
                                                  (igraph_integer_t) cand2, arg)) {
                end = 1;
            }

            for (i = 0; !end && i < igraph_vector_size(inneis_1); i++) {
                long int node = (long int) VECTOR(*inneis_1)[i];
                if (VECTOR(*core_1)[node] >= 0) {
                    long int node2 = (long int) VECTOR(*core_1)[node];
                    /* check if there is a node2->cand2 edge */
                    if (!igraph_vector_binsearch2(inneis_2, node2)) {
                        end = 1;
                    } else if (edge_color1 || edge_compat_fn) {
                        igraph_integer_t eid1, eid2;
                        igraph_get_eid(graph1, &eid1, (igraph_integer_t) node,
                                       (igraph_integer_t) cand1, /*directed=*/ 1,
                                       /*error=*/ 1);
                        igraph_get_eid(graph2, &eid2, (igraph_integer_t) node2,
                                       (igraph_integer_t) cand2, /*directed=*/ 1,
                                       /*error=*/ 1);
                        if (edge_color1 && VECTOR(*edge_color1)[(long int)eid1] !=
                            VECTOR(*edge_color2)[(long int)eid2]) {
                            end = 1;
                        }
                        if (edge_compat_fn && !edge_compat_fn(graph1, graph2,
                                                              eid1, eid2, arg)) {
                            end = 1;
                        }
                    }
                } else {
                    if (VECTOR(in_1)[node] != 0) {
                        xin1++;
                    }
                    if (VECTOR(out_1)[node] != 0) {
                        xout1++;
                    }
                }
            }
            for (i = 0; !end && i < igraph_vector_size(outneis_1); i++) {
                long int node = (long int) VECTOR(*outneis_1)[i];
                if (VECTOR(*core_1)[node] >= 0) {
                    long int node2 = (long int) VECTOR(*core_1)[node];
                    /* check if there is a cand2->node2 edge */
                    if (!igraph_vector_binsearch2(outneis_2, node2)) {
                        end = 1;
                    } else if (edge_color1 || edge_compat_fn) {
                        igraph_integer_t eid1, eid2;
                        igraph_get_eid(graph1, &eid1, (igraph_integer_t) cand1,
                                       (igraph_integer_t) node, /*directed=*/ 1,
                                       /*error=*/ 1);
                        igraph_get_eid(graph2, &eid2, (igraph_integer_t) cand2,
                                       (igraph_integer_t) node2, /*directed=*/ 1,
                                       /*error=*/ 1);
                        if (edge_color1 && VECTOR(*edge_color1)[(long int)eid1] !=
                            VECTOR(*edge_color2)[(long int)eid2]) {
                            end = 1;
                        }
                        if (edge_compat_fn && !edge_compat_fn(graph1, graph2,
                                                              eid1, eid2, arg)) {
                            end = 1;
                        }
                    }
                } else {
                    if (VECTOR(in_1)[node] != 0) {
                        xin1++;
                    }
                    if (VECTOR(out_1)[node] != 0) {
                        xout1++;
                    }
                }
            }
            for (i = 0; !end && i < igraph_vector_size(inneis_2); i++) {
                long int node = (long int) VECTOR(*inneis_2)[i];
                if (VECTOR(*core_2)[node] >= 0) {
                    long int node2 = (long int) VECTOR(*core_2)[node];
                    /* check if there is a node2->cand1 edge */
                    if (!igraph_vector_binsearch2(inneis_1, node2)) {
                        end = 1;
                    } else if (edge_color1 || edge_compat_fn) {
                        igraph_integer_t eid1, eid2;
                        igraph_get_eid(graph1, &eid1, (igraph_integer_t) node2,
                                       (igraph_integer_t) cand1, /*directed=*/ 1,
                                       /*error=*/ 1);
                        igraph_get_eid(graph2, &eid2, (igraph_integer_t) node,
                                       (igraph_integer_t) cand2, /*directed=*/ 1,
                                       /*error=*/ 1);
                        if (edge_color1 && VECTOR(*edge_color1)[(long int)eid1] !=
                            VECTOR(*edge_color2)[(long int)eid2]) {
                            end = 1;
                        }
                        if (edge_compat_fn && !edge_compat_fn(graph1, graph2,
                                                              eid1, eid2, arg)) {
                            end = 1;
                        }
                    }
                } else {
                    if (VECTOR(in_2)[node] != 0) {
                        xin2++;
                    }
                    if (VECTOR(out_2)[node] != 0) {
                        xout2++;
                    }
                }
            }
            for (i = 0; !end && i < igraph_vector_size(outneis_2); i++) {
                long int node = (long int) VECTOR(*outneis_2)[i];
                if (VECTOR(*core_2)[node] >= 0) {
                    long int node2 = (long int) VECTOR(*core_2)[node];
                    /* check if there is a cand1->node2 edge */
                    if (!igraph_vector_binsearch2(outneis_1, node2)) {
                        end = 1;
                    } else if (edge_color1 || edge_compat_fn) {
                        igraph_integer_t eid1, eid2;
                        igraph_get_eid(graph1, &eid1, (igraph_integer_t) cand1,
                                       (igraph_integer_t) node2, /*directed=*/ 1,
                                       /*error=*/ 1);
                        igraph_get_eid(graph2, &eid2, (igraph_integer_t) cand2,
                                       (igraph_integer_t) node, /*directed=*/ 1,
                                       /*error=*/ 1);
                        if (edge_color1 && VECTOR(*edge_color1)[(long int)eid1] !=
                            VECTOR(*edge_color2)[(long int)eid2]) {
                            end = 1;
                        }
                        if (edge_compat_fn && !edge_compat_fn(graph1, graph2,
                                                              eid1, eid2, arg)) {
                            end = 1;
                        }
                    }
                } else {
                    if (VECTOR(in_2)[node] != 0) {
                        xin2++;
                    }
                    if (VECTOR(out_2)[node] != 0) {
                        xout2++;
                    }
                }
            }

            if (!end && (xin1 == xin2 && xout1 == xout2)) {
                /* Ok, we add the (cand1, cand2) pair to the mapping */
                depth += 1;
                IGRAPH_CHECK(igraph_stack_push(&path, cand1));
                IGRAPH_CHECK(igraph_stack_push(&path, cand2));
                matched_nodes += 1;
                VECTOR(*core_1)[cand1] = cand2;
                VECTOR(*core_2)[cand2] = cand1;

                /* update in_*, out_* */
                if (VECTOR(in_1)[cand1] != 0) {
                    in_1_size -= 1;
                }
                if (VECTOR(out_1)[cand1] != 0) {
                    out_1_size -= 1;
                }
                if (VECTOR(in_2)[cand2] != 0) {
                    in_2_size -= 1;
                }
                if (VECTOR(out_2)[cand2] != 0) {
                    out_2_size -= 1;
                }

                inneis_1 = igraph_lazy_adjlist_get(&inadj1, (igraph_integer_t) cand1);
                for (i = 0; i < igraph_vector_size(inneis_1); i++) {
                    long int node = (long int) VECTOR(*inneis_1)[i];
                    if (VECTOR(in_1)[node] == 0 && VECTOR(*core_1)[node] < 0) {
                        VECTOR(in_1)[node] = depth;
                        in_1_size += 1;
                    }
                }
                outneis_1 = igraph_lazy_adjlist_get(&outadj1, (igraph_integer_t) cand1);
                for (i = 0; i < igraph_vector_size(outneis_1); i++) {
                    long int node = (long int) VECTOR(*outneis_1)[i];
                    if (VECTOR(out_1)[node] == 0 && VECTOR(*core_1)[node] < 0) {
                        VECTOR(out_1)[node] = depth;
                        out_1_size += 1;
                    }
                }
                inneis_2 = igraph_lazy_adjlist_get(&inadj2, (igraph_integer_t) cand2);
                for (i = 0; i < igraph_vector_size(inneis_2); i++) {
                    long int node = (long int) VECTOR(*inneis_2)[i];
                    if (VECTOR(in_2)[node] == 0 && VECTOR(*core_2)[node] < 0) {
                        VECTOR(in_2)[node] = depth;
                        in_2_size += 1;
                    }
                }
                outneis_2 = igraph_lazy_adjlist_get(&outadj2, (igraph_integer_t) cand2);
                for (i = 0; i < igraph_vector_size(outneis_2); i++) {
                    long int node = (long int) VECTOR(*outneis_2)[i];
                    if (VECTOR(out_2)[node] == 0 && VECTOR(*core_2)[node] < 0) {
                        VECTOR(out_2)[node] = depth;
                        out_2_size += 1;
                    }
                }
                last1 = -1; last2 = -1;       /* this the first time here */
            } else {
                last1 = cand1;
                last2 = cand2;
            }

        }

        if (matched_nodes == no_of_nodes && isohandler_fn) {
            if (!isohandler_fn(core_1, core_2, arg)) {
                break;
            }
        }
    }

    igraph_vector_destroy(&outdeg2);
    igraph_vector_destroy(&outdeg1);
    igraph_vector_destroy(&indeg2);
    igraph_vector_destroy(&indeg1);
    igraph_lazy_adjlist_destroy(&outadj2);
    igraph_lazy_adjlist_destroy(&inadj2);
    igraph_lazy_adjlist_destroy(&outadj1);
    igraph_lazy_adjlist_destroy(&inadj1);
    igraph_stack_destroy(&path);
    igraph_vector_destroy(&out_2);
    igraph_vector_destroy(&out_1);
    igraph_vector_destroy(&in_2);
    igraph_vector_destroy(&in_1);
    IGRAPH_FINALLY_CLEAN(13);
    if (!map21) {
        igraph_vector_destroy(core_2);
        IGRAPH_FINALLY_CLEAN(1);
    }
    if (!map12) {
        igraph_vector_destroy(core_1);
        IGRAPH_FINALLY_CLEAN(1);
    }

    return 0;
}

typedef struct {
    igraph_isocompat_t *node_compat_fn, *edge_compat_fn;
    void *arg, *carg;
} igraph_i_iso_cb_data_t;

static igraph_bool_t igraph_i_isocompat_node_cb(
        const igraph_t *graph1,
        const igraph_t *graph2,
        const igraph_integer_t g1_num,
        const igraph_integer_t g2_num,
        void *arg) {
    igraph_i_iso_cb_data_t *data = arg;
    return data->node_compat_fn(graph1, graph2, g1_num, g2_num, data->carg);
}

static igraph_bool_t igraph_i_isocompat_edge_cb(
        const igraph_t *graph1,
        const igraph_t *graph2,
        const igraph_integer_t g1_num,
        const igraph_integer_t g2_num,
        void *arg) {
    igraph_i_iso_cb_data_t *data = arg;
    return data->edge_compat_fn(graph1, graph2, g1_num, g2_num, data->carg);
}

static igraph_bool_t igraph_i_isomorphic_vf2(igraph_vector_t *map12,
                                             igraph_vector_t *map21,
                                             void *arg) {
    igraph_i_iso_cb_data_t *data = arg;
    igraph_bool_t *iso = data->arg;
    IGRAPH_UNUSED(map12); IGRAPH_UNUSED(map21);
    *iso = 1;
    return 0;         /* don't need to continue */
}

/**
 * \function igraph_isomorphic_vf2
 * \brief Isomorphism via VF2
 *
 * </para><para>
 * This function performs the VF2 algorithm via calling \ref
 * igraph_isomorphic_function_vf2().
 *
 * </para><para> Note that this function cannot be used for
 * deciding subgraph isomorphism, use \ref igraph_subisomorphic_vf2()
 * for that.
 * \param graph1 The first graph, may be directed or undirected.
 * \param graph2 The second graph. It must have the same directedness
 *    as \p graph1, otherwise an error is reported.
 * \param vertex_color1 An optional color vector for the first graph. If
 *   color vectors are given for both graphs, then the isomorphism is
 *   calculated on the colored graphs; i.e. two vertices can match
 *   only if their color also matches. Supply a null pointer here if
 *   your graphs are not colored.
 * \param vertex_color2 An optional color vector for the second graph. See
 *   the previous argument for explanation.
 * \param edge_color1 An optional edge color vector for the first
 *   graph. The matching edges in the two graphs must have matching
 *   colors as well. Supply a null pointer here if your graphs are not
 *   edge-colored.
 * \param edge_color2 The edge color vector for the second graph.
 * \param iso Pointer to a logical constant, the result of the
 *    algorithm will be placed here.
 * \param map12 Pointer to an initialized vector or a NULL pointer. If not
 *    a NULL pointer then the mapping from \p graph1 to \p graph2 is
 *    stored here. If the graphs are not isomorphic then the vector is
 *    cleared (i.e. has zero elements).
 * \param map21 Pointer to an initialized vector or a NULL pointer. If not
 *    a NULL pointer then the mapping from \p graph2 to \p graph1 is
 *    stored here. If the graphs are not isomorphic then the vector is
 *    cleared (i.e. has zero elements).
 * \param node_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two nodes are compatible.
 * \param edge_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two edges are compatible.
 * \param arg Extra argument to supply to functions \p node_compat_fn
 *   and \p edge_compat_fn.
 * \return Error code.
 *
 * \sa \ref igraph_subisomorphic_vf2(),
 * \ref igraph_count_isomorphisms_vf2(),
 * \ref igraph_get_isomorphisms_vf2(),
 *
 * Time complexity: exponential, what did you expect?
 *
 * \example examples/simple/igraph_isomorphic_vf2.c
 */

int igraph_isomorphic_vf2(const igraph_t *graph1, const igraph_t *graph2,
                          const igraph_vector_int_t *vertex_color1,
                          const igraph_vector_int_t *vertex_color2,
                          const igraph_vector_int_t *edge_color1,
                          const igraph_vector_int_t *edge_color2,
                          igraph_bool_t *iso, igraph_vector_t *map12,
                          igraph_vector_t *map21,
                          igraph_isocompat_t *node_compat_fn,
                          igraph_isocompat_t *edge_compat_fn,
                          void *arg) {

    igraph_i_iso_cb_data_t data = { node_compat_fn, edge_compat_fn, iso, arg };
    igraph_isocompat_t *ncb = node_compat_fn ? igraph_i_isocompat_node_cb : 0;
    igraph_isocompat_t *ecb = edge_compat_fn ? igraph_i_isocompat_edge_cb : 0;
    *iso = 0;
    IGRAPH_CHECK(igraph_isomorphic_function_vf2(graph1, graph2,
                 vertex_color1, vertex_color2,
                 edge_color1, edge_color2,
                 map12, map21,
                 (igraph_isohandler_t*)
                 igraph_i_isomorphic_vf2,
                 ncb, ecb, &data));
    if (! *iso) {
        if (map12) {
            igraph_vector_clear(map12);
        }
        if (map21) {
            igraph_vector_clear(map21);
        }
    }
    return 0;
}

static igraph_bool_t igraph_i_count_isomorphisms_vf2(
        const igraph_vector_t *map12,
        const igraph_vector_t *map21,
        void *arg) {
    igraph_i_iso_cb_data_t *data = arg;
    igraph_integer_t *count = data->arg;
    IGRAPH_UNUSED(map12); IGRAPH_UNUSED(map21);
    *count += 1;
    return 1;         /* always continue */
}

/**
 * \function igraph_count_isomorphisms_vf2
 * Number of isomorphisms via VF2
 *
 * This function counts the number of isomorphic mappings between two
 * graphs. It uses the generic \ref igraph_isomorphic_function_vf2()
 * function.
 * \param graph1 The first input graph, may be directed or undirected.
 * \param graph2 The second input graph, it must have the same
 *   directedness as \p graph1, or an error will be reported.
 * \param vertex_color1 An optional color vector for the first graph. If
 *   color vectors are given for both graphs, then the isomorphism is
 *   calculated on the colored graphs; i.e. two vertices can match
 *   only if their color also matches. Supply a null pointer here if
 *   your graphs are not colored.
 * \param vertex_color2 An optional color vector for the second graph. See
 *   the previous argument for explanation.
 * \param edge_color1 An optional edge color vector for the first
 *   graph. The matching edges in the two graphs must have matching
 *   colors as well. Supply a null pointer here if your graphs are not
 *   edge-colored.
 * \param edge_color2 The edge color vector for the second graph.
 * \param count Point to an integer, the result will be stored here.
 * \param node_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two nodes are compatible.
 * \param edge_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two edges are compatible.
 * \param arg Extra argument to supply to functions \p node_compat_fn and
 *   \p edge_compat_fn.
 * \return Error code.
 *
 * Time complexity: exponential.
 */

int igraph_count_isomorphisms_vf2(const igraph_t *graph1, const igraph_t *graph2,
                                  const igraph_vector_int_t *vertex_color1,
                                  const igraph_vector_int_t *vertex_color2,
                                  const igraph_vector_int_t *edge_color1,
                                  const igraph_vector_int_t *edge_color2,
                                  igraph_integer_t *count,
                                  igraph_isocompat_t *node_compat_fn,
                                  igraph_isocompat_t *edge_compat_fn,
                                  void *arg) {

    igraph_i_iso_cb_data_t data = { node_compat_fn, edge_compat_fn,
                                    count, arg
                                  };
    igraph_isocompat_t *ncb = node_compat_fn ? igraph_i_isocompat_node_cb : 0;
    igraph_isocompat_t *ecb = edge_compat_fn ? igraph_i_isocompat_edge_cb : 0;
    *count = 0;
    IGRAPH_CHECK(igraph_isomorphic_function_vf2(graph1, graph2,
                 vertex_color1, vertex_color2,
                 edge_color1, edge_color2,
                 0, 0,
                 (igraph_isohandler_t*)
                 igraph_i_count_isomorphisms_vf2,
                 ncb, ecb, &data));
    return 0;
}

static void igraph_i_get_isomorphisms_free(igraph_vector_ptr_t *data) {
    long int i, n = igraph_vector_ptr_size(data);
    for (i = 0; i < n; i++) {
        igraph_vector_t *vec = VECTOR(*data)[i];
        igraph_vector_destroy(vec);
        igraph_free(vec);
    }
}

static igraph_bool_t igraph_i_get_isomorphisms_vf2(
        const igraph_vector_t *map12,
        const igraph_vector_t *map21,
        void *arg) {

    igraph_i_iso_cb_data_t *data = arg;
    igraph_vector_ptr_t *ptrvector = data->arg;
    igraph_vector_t *newvector = igraph_Calloc(1, igraph_vector_t);
    IGRAPH_UNUSED(map12);
    if (!newvector) {
        igraph_error("Out of memory", __FILE__, __LINE__, IGRAPH_ENOMEM);
        return 0;           /* stop right here */
    }
    IGRAPH_FINALLY(igraph_free, newvector);
    IGRAPH_CHECK(igraph_vector_copy(newvector, map21));
    IGRAPH_FINALLY(igraph_vector_destroy, newvector);
    IGRAPH_CHECK(igraph_vector_ptr_push_back(ptrvector, newvector));
    IGRAPH_FINALLY_CLEAN(2);

    return 1;         /* continue finding subisomorphisms */
}

/**
 * \function igraph_get_isomorphisms_vf2
 * Collect the isomorphic mappings
 *
 * This function finds all the isomorphic mappings between two
 * graphs. It uses the \ref igraph_isomorphic_function_vf2()
 * function. Call the function with the same graph as \p graph1 and \p
 * graph2 to get automorphisms.
 * \param graph1 The first input graph, may be directed or undirected.
 * \param graph2 The second input graph, it must have the same
 *   directedness as \p graph1, or an error will be reported.
 * \param vertex_color1 An optional color vector for the first graph. If
 *   color vectors are given for both graphs, then the isomorphism is
 *   calculated on the colored graphs; i.e. two vertices can match
 *   only if their color also matches. Supply a null pointer here if
 *   your graphs are not colored.
 * \param vertex_color2 An optional color vector for the second graph. See
 *   the previous argument for explanation.
 * \param edge_color1 An optional edge color vector for the first
 *   graph. The matching edges in the two graphs must have matching
 *   colors as well. Supply a null pointer here if your graphs are not
 *   edge-colored.
 * \param edge_color2 The edge color vector for the second graph.
 * \param maps Pointer vector. On return it is empty if the input graphs
 *   are no isomorphic. Otherwise it contains pointers to
 *   \ref igraph_vector_t objects, each vector is an
 *   isomorphic mapping of \p graph2 to \p graph1. Please note that
 *   you need to 1) Destroy the vectors via \ref
 *   igraph_vector_destroy(), 2) free them via
 *   \ref igraph_free() and then 3) call \ref
 *   igraph_vector_ptr_destroy() on the pointer vector to deallocate all
 *   memory when \p maps is no longer needed.
 * \param node_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two nodes are compatible.
 * \param edge_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two edges are compatible.
 * \param arg Extra argument to supply to functions \p node_compat_fn
 *   and \p edge_compat_fn.
 * \return Error code.
 *
 * Time complexity: exponential.
 */

int igraph_get_isomorphisms_vf2(const igraph_t *graph1,
                                const igraph_t *graph2,
                                const igraph_vector_int_t *vertex_color1,
                                const igraph_vector_int_t *vertex_color2,
                                const igraph_vector_int_t *edge_color1,
                                const igraph_vector_int_t *edge_color2,
                                igraph_vector_ptr_t *maps,
                                igraph_isocompat_t *node_compat_fn,
                                igraph_isocompat_t *edge_compat_fn,
                                void *arg) {

    igraph_i_iso_cb_data_t data = { node_compat_fn, edge_compat_fn, maps, arg };
    igraph_isocompat_t *ncb = node_compat_fn ? igraph_i_isocompat_node_cb : 0;
    igraph_isocompat_t *ecb = edge_compat_fn ? igraph_i_isocompat_edge_cb : 0;

    igraph_vector_ptr_clear(maps);
    IGRAPH_FINALLY(igraph_i_get_isomorphisms_free, maps);
    IGRAPH_CHECK(igraph_isomorphic_function_vf2(graph1, graph2,
                 vertex_color1, vertex_color2,
                 edge_color1, edge_color2,
                 0, 0,
                 (igraph_isohandler_t*)
                 igraph_i_get_isomorphisms_vf2,
                 ncb, ecb, &data));
    IGRAPH_FINALLY_CLEAN(1);
    return 0;
}


/**
 * \function igraph_subisomorphic
 * Decide subgraph isomorphism
 *
 * Check whether \p graph2 is isomorphic to a subgraph of \p graph1.
 * Currently this function just calls \ref igraph_subisomorphic_vf2()
 * for all graphs.
 * \param graph1 The first input graph, may be directed or
 *   undirected. This is supposed to be the bigger graph.
 * \param graph2 The second input graph, it must have the same
 *   directedness as \p graph2, or an error is triggered. This is
 *   supposed to be the smaller graph.
 * \param iso Pointer to a boolean, the result is stored here.
 * \return Error code.
 *
 * Time complexity: exponential.
 */

int igraph_subisomorphic(const igraph_t *graph1, const igraph_t *graph2,
                         igraph_bool_t *iso) {

    return igraph_subisomorphic_vf2(graph1, graph2, 0, 0, 0, 0, iso, 0, 0, 0, 0, 0);
}

/**
 * \function igraph_subisomorphic_function_vf2
 * Generic VF2 function for subgraph isomorphism problems
 *
 * This function is the pair of \ref igraph_isomorphic_function_vf2(),
 * for subgraph isomorphism problems. It searches for subgraphs of \p
 * graph1 which are isomorphic to \p graph2. When it founds an
 * isomorphic mapping it calls the supplied callback \p isohandler_fn.
 * The mapping (and its inverse) and the additional \p arg argument
 * are supplied to the callback.
 * \param graph1 The first input graph, may be directed or
 *    undirected. This is supposed to be the larger graph.
 * \param graph2 The second input graph, it must have the same
 *    directedness as \p graph1. This is supposed to be the smaller
 *    graph.
 * \param vertex_color1 An optional color vector for the first graph. If
 *   color vectors are given for both graphs, then the subgraph isomorphism is
 *   calculated on the colored graphs; i.e. two vertices can match
 *   only if their color also matches. Supply a null pointer here if
 *   your graphs are not colored.
 * \param vertex_color2 An optional color vector for the second graph. See
 *   the previous argument for explanation.
 * \param edge_color1 An optional edge color vector for the first
 *   graph. The matching edges in the two graphs must have matching
 *   colors as well. Supply a null pointer here if your graphs are not
 *   edge-colored.
 * \param edge_color2 The edge color vector for the second graph.
 * \param map12 Pointer to a vector or \c NULL. If not \c NULL, then an
 *    isomorphic mapping from \p graph1 to \p graph2 is stored here.
 * \param map21 Pointer to a vector ot \c NULL. If not \c NULL, then
 *    an isomorphic mapping from \p graph2 to \p graph1 is stored
 *    here.
 * \param isohandler_fn A pointer to a function of type \ref
 *   igraph_isohandler_t. This will be called whenever a subgraph
 *   isomorphism is found. If the function returns with a non-zero value
 *   then the search is continued, otherwise it stops and the function
 *   returns.
 * \param node_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two nodes are compatible.
 * \param edge_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two edges are compatible.
 * \param arg Extra argument to supply to functions \p isohandler_fn, \p
 *   node_compat_fn and \p edge_compat_fn.
 * \return Error code.
 *
 * Time complexity: exponential.
 */

int igraph_subisomorphic_function_vf2(const igraph_t *graph1,
                                      const igraph_t *graph2,
                                      const igraph_vector_int_t *vertex_color1,
                                      const igraph_vector_int_t *vertex_color2,
                                      const igraph_vector_int_t *edge_color1,
                                      const igraph_vector_int_t *edge_color2,
                                      igraph_vector_t *map12,
                                      igraph_vector_t *map21,
                                      igraph_isohandler_t *isohandler_fn,
                                      igraph_isocompat_t *node_compat_fn,
                                      igraph_isocompat_t *edge_compat_fn,
                                      void *arg) {

    long int no_of_nodes1 = igraph_vcount(graph1),
             no_of_nodes2 = igraph_vcount(graph2);
    long int no_of_edges1 = igraph_ecount(graph1),
             no_of_edges2 = igraph_ecount(graph2);
    igraph_vector_t mycore_1, mycore_2, *core_1 = &mycore_1, *core_2 = &mycore_2;
    igraph_vector_t in_1, in_2, out_1, out_2;
    long int in_1_size = 0, in_2_size = 0, out_1_size = 0, out_2_size = 0;
    igraph_vector_t *inneis_1, *inneis_2, *outneis_1, *outneis_2;
    long int matched_nodes = 0;
    long int depth;
    long int cand1, cand2;
    long int last1, last2;
    igraph_stack_t path;
    igraph_lazy_adjlist_t inadj1, inadj2, outadj1, outadj2;
    igraph_vector_t indeg1, indeg2, outdeg1, outdeg2;

    if (igraph_is_directed(graph1) != igraph_is_directed(graph2)) {
        IGRAPH_ERROR("Cannot compare directed and undirected graphs",
                     IGRAPH_EINVAL);
    }

    if (no_of_nodes1 < no_of_nodes2 ||
        no_of_edges1 < no_of_edges2) {
        return 0;
    }

    if ( (vertex_color1 && !vertex_color2) || (!vertex_color1 && vertex_color2) ) {
        IGRAPH_WARNING("Only one graph is vertex colored, colors will be ignored");
        vertex_color1 = vertex_color2 = 0;
    }

    if ( (edge_color1 && !edge_color2) || (!edge_color1 && edge_color2) ) {
        IGRAPH_WARNING("Only one graph is edge colored, colors will be ignored");
        edge_color1 = edge_color2 = 0;
    }

    if (vertex_color1) {
        if (igraph_vector_int_size(vertex_color1) != no_of_nodes1 ||
            igraph_vector_int_size(vertex_color2) != no_of_nodes2) {
            IGRAPH_ERROR("Invalid vertex color vector length", IGRAPH_EINVAL);
        }
    }

    if (edge_color1) {
        if (igraph_vector_int_size(edge_color1) != no_of_edges1 ||
            igraph_vector_int_size(edge_color2) != no_of_edges2) {
            IGRAPH_ERROR("Invalid edge color vector length", IGRAPH_EINVAL);
        }
    }

    /* Check color distribution */
    if (vertex_color1) {
        /* TODO */
    }

    /* Check edge color distribution */
    if (edge_color1) {
        /* TODO */
    }

    if (map12) {
        core_1 = map12;
        IGRAPH_CHECK(igraph_vector_resize(core_1, no_of_nodes1));
    } else {
        IGRAPH_VECTOR_INIT_FINALLY(core_1, no_of_nodes1);
    }
    igraph_vector_fill(core_1, -1);
    if (map21) {
        core_2 = map21;
        IGRAPH_CHECK(igraph_vector_resize(core_2, no_of_nodes2));
    } else {
        IGRAPH_VECTOR_INIT_FINALLY(core_2, no_of_nodes2);
    }
    igraph_vector_fill(core_2, -1);
    IGRAPH_VECTOR_INIT_FINALLY(&in_1, no_of_nodes1);
    IGRAPH_VECTOR_INIT_FINALLY(&in_2, no_of_nodes2);
    IGRAPH_VECTOR_INIT_FINALLY(&out_1, no_of_nodes1);
    IGRAPH_VECTOR_INIT_FINALLY(&out_2, no_of_nodes2);
    IGRAPH_CHECK(igraph_stack_init(&path, 0));
    IGRAPH_FINALLY(igraph_stack_destroy, &path);
    IGRAPH_CHECK(igraph_lazy_adjlist_init(graph1, &inadj1, IGRAPH_IN,
                                          IGRAPH_SIMPLIFY));
    IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &inadj1);
    IGRAPH_CHECK(igraph_lazy_adjlist_init(graph1, &outadj1, IGRAPH_OUT,
                                          IGRAPH_SIMPLIFY));
    IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &outadj1);
    IGRAPH_CHECK(igraph_lazy_adjlist_init(graph2, &inadj2, IGRAPH_IN,
                                          IGRAPH_SIMPLIFY));
    IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &inadj2);
    IGRAPH_CHECK(igraph_lazy_adjlist_init(graph2, &outadj2, IGRAPH_OUT,
                                          IGRAPH_SIMPLIFY));
    IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &outadj2);
    IGRAPH_VECTOR_INIT_FINALLY(&indeg1, 0);
    IGRAPH_VECTOR_INIT_FINALLY(&indeg2, 0);
    IGRAPH_VECTOR_INIT_FINALLY(&outdeg1, 0);
    IGRAPH_VECTOR_INIT_FINALLY(&outdeg2, 0);

    IGRAPH_CHECK(igraph_stack_reserve(&path, no_of_nodes2 * 2));
    IGRAPH_CHECK(igraph_degree(graph1, &indeg1, igraph_vss_all(),
                               IGRAPH_IN, IGRAPH_LOOPS));
    IGRAPH_CHECK(igraph_degree(graph2, &indeg2, igraph_vss_all(),
                               IGRAPH_IN, IGRAPH_LOOPS));
    IGRAPH_CHECK(igraph_degree(graph1, &outdeg1, igraph_vss_all(),
                               IGRAPH_OUT, IGRAPH_LOOPS));
    IGRAPH_CHECK(igraph_degree(graph2, &outdeg2, igraph_vss_all(),
                               IGRAPH_OUT, IGRAPH_LOOPS));

    depth = 0; last1 = -1; last2 = -1;
    while (depth >= 0) {
        long int i;

        IGRAPH_ALLOW_INTERRUPTION();

        cand1 = -1; cand2 = -1;
        /* Search for the next pair to try */
        if ((in_1_size < in_2_size) ||
            (out_1_size < out_2_size)) {
            /* step back, nothing to do */
        } else if (out_1_size > 0 && out_2_size > 0) {
            /**************************************************************/
            /* cand2, search not always needed */
            if (last2 >= 0) {
                cand2 = last2;
            } else {
                i = 0;
                while (cand2 < 0 && i < no_of_nodes2) {
                    if (VECTOR(out_2)[i] > 0 && VECTOR(*core_2)[i] < 0) {
                        cand2 = i;
                    }
                    i++;
                }
            }
            /* search for cand1 now, it should be bigger than last1 */
            i = last1 + 1;
            while (cand1 < 0 && i < no_of_nodes1) {
                if (VECTOR(out_1)[i] > 0 && VECTOR(*core_1)[i] < 0) {
                    cand1 = i;
                }
                i++;
            }
        } else if (in_1_size > 0 && in_2_size > 0) {
            /**************************************************************/
            /* cand2, search not always needed */
            if (last2 >= 0) {
                cand2 = last2;
            } else {
                i = 0;
                while (cand2 < 0 && i < no_of_nodes2) {
                    if (VECTOR(in_2)[i] > 0 && VECTOR(*core_2)[i] < 0) {
                        cand2 = i;
                    }
                    i++;
                }
            }
            /* search for cand1 now, should be bigger than last1 */
            i = last1 + 1;
            while (cand1 < 0 && i < no_of_nodes1) {
                if (VECTOR(in_1)[i] > 0 && VECTOR(*core_1)[i] < 0) {
                    cand1 = i;
                }
                i++;
            }
        } else {
            /**************************************************************/
            /* cand2, search not always needed */
            if (last2 >= 0) {
                cand2 = last2;
            } else {
                i = 0;
                while (cand2 < 0 && i < no_of_nodes2) {
                    if (VECTOR(*core_2)[i] < 0) {
                        cand2 = i;
                    }
                    i++;
                }
            }
            /* search for cand1, should be bigger than last1 */
            i = last1 + 1;
            while (cand1 < 0 && i < no_of_nodes1) {
                if (VECTOR(*core_1)[i] < 0) {
                    cand1 = i;
                }
                i++;
            }
        }

        /* Ok, we have cand1, cand2 as candidates. Or not? */
        if (cand1 < 0 || cand2 < 0) {
            /**************************************************************/
            /* dead end, step back, if possible. Otherwise we'll terminate */
            if (depth >= 1) {
                last2 = (long int) igraph_stack_pop(&path);
                last1 = (long int) igraph_stack_pop(&path);
                matched_nodes -= 1;
                VECTOR(*core_1)[last1] = -1;
                VECTOR(*core_2)[last2] = -1;

                if (VECTOR(in_1)[last1] != 0) {
                    in_1_size += 1;
                }
                if (VECTOR(out_1)[last1] != 0) {
                    out_1_size += 1;
                }
                if (VECTOR(in_2)[last2] != 0) {
                    in_2_size += 1;
                }
                if (VECTOR(out_2)[last2] != 0) {
                    out_2_size += 1;
                }

                inneis_1 = igraph_lazy_adjlist_get(&inadj1, (igraph_integer_t) last1);
                for (i = 0; i < igraph_vector_size(inneis_1); i++) {
                    long int node = (long int) VECTOR(*inneis_1)[i];
                    if (VECTOR(in_1)[node] == depth) {
                        VECTOR(in_1)[node] = 0;
                        in_1_size -= 1;
                    }
                }
                outneis_1 = igraph_lazy_adjlist_get(&outadj1, (igraph_integer_t) last1);
                for (i = 0; i < igraph_vector_size(outneis_1); i++) {
                    long int node = (long int) VECTOR(*outneis_1)[i];
                    if (VECTOR(out_1)[node] == depth) {
                        VECTOR(out_1)[node] = 0;
                        out_1_size -= 1;
                    }
                }
                inneis_2 = igraph_lazy_adjlist_get(&inadj2, (igraph_integer_t) last2);
                for (i = 0; i < igraph_vector_size(inneis_2); i++) {
                    long int node = (long int) VECTOR(*inneis_2)[i];
                    if (VECTOR(in_2)[node] == depth) {
                        VECTOR(in_2)[node] = 0;
                        in_2_size -= 1;
                    }
                }
                outneis_2 = igraph_lazy_adjlist_get(&outadj2, (igraph_integer_t) last2);
                for (i = 0; i < igraph_vector_size(outneis_2); i++) {
                    long int node = (long int) VECTOR(*outneis_2)[i];
                    if (VECTOR(out_2)[node] == depth) {
                        VECTOR(out_2)[node] = 0;
                        out_2_size -= 1;
                    }
                }

            } /* end of stepping back */

            depth -= 1;

        } else {
            /**************************************************************/
            /* step forward if worth, check if worth first */
            long int xin1 = 0, xin2 = 0, xout1 = 0, xout2 = 0;
            igraph_bool_t end = 0;
            inneis_1 = igraph_lazy_adjlist_get(&inadj1, (igraph_integer_t) cand1);
            outneis_1 = igraph_lazy_adjlist_get(&outadj1, (igraph_integer_t) cand1);
            inneis_2 = igraph_lazy_adjlist_get(&inadj2, (igraph_integer_t) cand2);
            outneis_2 = igraph_lazy_adjlist_get(&outadj2, (igraph_integer_t) cand2);
            if (VECTOR(indeg1)[cand1] < VECTOR(indeg2)[cand2] ||
                VECTOR(outdeg1)[cand1] < VECTOR(outdeg2)[cand2]) {
                end = 1;
            }
            if (vertex_color1 && VECTOR(*vertex_color1)[cand1] != VECTOR(*vertex_color2)[cand2]) {
                end = 1;
            }
            if (node_compat_fn && !node_compat_fn(graph1, graph2,
                                                  (igraph_integer_t) cand1,
                                                  (igraph_integer_t) cand2, arg)) {
                end = 1;
            }

            for (i = 0; !end && i < igraph_vector_size(inneis_1); i++) {
                long int node = (long int) VECTOR(*inneis_1)[i];
                if (VECTOR(*core_1)[node] < 0) {
                    if (VECTOR(in_1)[node] != 0) {
                        xin1++;
                    }
                    if (VECTOR(out_1)[node] != 0) {
                        xout1++;
                    }
                }
            }
            for (i = 0; !end && i < igraph_vector_size(outneis_1); i++) {
                long int node = (long int) VECTOR(*outneis_1)[i];
                if (VECTOR(*core_1)[node] < 0) {
                    if (VECTOR(in_1)[node] != 0) {
                        xin1++;
                    }
                    if (VECTOR(out_1)[node] != 0) {
                        xout1++;
                    }
                }
            }
            for (i = 0; !end && i < igraph_vector_size(inneis_2); i++) {
                long int node = (long int) VECTOR(*inneis_2)[i];
                if (VECTOR(*core_2)[node] >= 0) {
                    long int node2 = (long int) VECTOR(*core_2)[node];
                    /* check if there is a node2->cand1 edge */
                    if (!igraph_vector_binsearch2(inneis_1, node2)) {
                        end = 1;
                    } else if (edge_color1 || edge_compat_fn) {
                        igraph_integer_t eid1, eid2;
                        igraph_get_eid(graph1, &eid1, (igraph_integer_t) node2,
                                       (igraph_integer_t) cand1, /*directed=*/ 1,
                                       /*error=*/ 1);
                        igraph_get_eid(graph2, &eid2, (igraph_integer_t) node,
                                       (igraph_integer_t) cand2, /*directed=*/ 1,
                                       /*error=*/ 1);
                        if (edge_color1 && VECTOR(*edge_color1)[(long int)eid1] !=
                            VECTOR(*edge_color2)[(long int)eid2]) {
                            end = 1;
                        }
                        if (edge_compat_fn && !edge_compat_fn(graph1, graph2,
                                                              eid1, eid2, arg)) {
                            end = 1;
                        }
                    }
                } else {
                    if (VECTOR(in_2)[node] != 0) {
                        xin2++;
                    }
                    if (VECTOR(out_2)[node] != 0) {
                        xout2++;
                    }
                }
            }
            for (i = 0; !end && i < igraph_vector_size(outneis_2); i++) {
                long int node = (long int) VECTOR(*outneis_2)[i];
                if (VECTOR(*core_2)[node] >= 0) {
                    long int node2 = (long int) VECTOR(*core_2)[node];
                    /* check if there is a cand1->node2 edge */
                    if (!igraph_vector_binsearch2(outneis_1, node2)) {
                        end = 1;
                    } else if (edge_color1 || edge_compat_fn) {
                        igraph_integer_t eid1, eid2;
                        igraph_get_eid(graph1, &eid1, (igraph_integer_t) cand1,
                                       (igraph_integer_t) node2, /*directed=*/ 1,
                                       /*error=*/ 1);
                        igraph_get_eid(graph2, &eid2, (igraph_integer_t) cand2,
                                       (igraph_integer_t) node, /*directed=*/ 1,
                                       /*error=*/ 1);
                        if (edge_color1 && VECTOR(*edge_color1)[(long int)eid1] !=
                            VECTOR(*edge_color2)[(long int)eid2]) {
                            end = 1;
                        }
                        if (edge_compat_fn && !edge_compat_fn(graph1, graph2,
                                                              eid1, eid2, arg)) {
                            end = 1;
                        }
                    }
                } else {
                    if (VECTOR(in_2)[node] != 0) {
                        xin2++;
                    }
                    if (VECTOR(out_2)[node] != 0) {
                        xout2++;
                    }
                }
            }

            if (!end && (xin1 >= xin2 && xout1 >= xout2)) {
                /* Ok, we add the (cand1, cand2) pair to the mapping */
                depth += 1;
                IGRAPH_CHECK(igraph_stack_push(&path, cand1));
                IGRAPH_CHECK(igraph_stack_push(&path, cand2));
                matched_nodes += 1;
                VECTOR(*core_1)[cand1] = cand2;
                VECTOR(*core_2)[cand2] = cand1;

                /* update in_*, out_* */
                if (VECTOR(in_1)[cand1] != 0) {
                    in_1_size -= 1;
                }
                if (VECTOR(out_1)[cand1] != 0) {
                    out_1_size -= 1;
                }
                if (VECTOR(in_2)[cand2] != 0) {
                    in_2_size -= 1;
                }
                if (VECTOR(out_2)[cand2] != 0) {
                    out_2_size -= 1;
                }

                inneis_1 = igraph_lazy_adjlist_get(&inadj1, (igraph_integer_t) cand1);
                for (i = 0; i < igraph_vector_size(inneis_1); i++) {
                    long int node = (long int) VECTOR(*inneis_1)[i];
                    if (VECTOR(in_1)[node] == 0 && VECTOR(*core_1)[node] < 0) {
                        VECTOR(in_1)[node] = depth;
                        in_1_size += 1;
                    }
                }
                outneis_1 = igraph_lazy_adjlist_get(&outadj1, (igraph_integer_t) cand1);
                for (i = 0; i < igraph_vector_size(outneis_1); i++) {
                    long int node = (long int) VECTOR(*outneis_1)[i];
                    if (VECTOR(out_1)[node] == 0 && VECTOR(*core_1)[node] < 0) {
                        VECTOR(out_1)[node] = depth;
                        out_1_size += 1;
                    }
                }
                inneis_2 = igraph_lazy_adjlist_get(&inadj2, (igraph_integer_t) cand2);
                for (i = 0; i < igraph_vector_size(inneis_2); i++) {
                    long int node = (long int) VECTOR(*inneis_2)[i];
                    if (VECTOR(in_2)[node] == 0 && VECTOR(*core_2)[node] < 0) {
                        VECTOR(in_2)[node] = depth;
                        in_2_size += 1;
                    }
                }
                outneis_2 = igraph_lazy_adjlist_get(&outadj2, (igraph_integer_t) cand2);
                for (i = 0; i < igraph_vector_size(outneis_2); i++) {
                    long int node = (long int) VECTOR(*outneis_2)[i];
                    if (VECTOR(out_2)[node] == 0 && VECTOR(*core_2)[node] < 0) {
                        VECTOR(out_2)[node] = depth;
                        out_2_size += 1;
                    }
                }
                last1 = -1; last2 = -1;       /* this the first time here */
            } else {
                last1 = cand1;
                last2 = cand2;
            }

        }

        if (matched_nodes == no_of_nodes2 && isohandler_fn) {
            if (!isohandler_fn(core_1, core_2, arg)) {
                break;
            }
        }
    }

    igraph_vector_destroy(&outdeg2);
    igraph_vector_destroy(&outdeg1);
    igraph_vector_destroy(&indeg2);
    igraph_vector_destroy(&indeg1);
    igraph_lazy_adjlist_destroy(&outadj2);
    igraph_lazy_adjlist_destroy(&inadj2);
    igraph_lazy_adjlist_destroy(&outadj1);
    igraph_lazy_adjlist_destroy(&inadj1);
    igraph_stack_destroy(&path);
    igraph_vector_destroy(&out_2);
    igraph_vector_destroy(&out_1);
    igraph_vector_destroy(&in_2);
    igraph_vector_destroy(&in_1);
    IGRAPH_FINALLY_CLEAN(13);
    if (!map21) {
        igraph_vector_destroy(core_2);
        IGRAPH_FINALLY_CLEAN(1);
    }
    if (!map12) {
        igraph_vector_destroy(core_1);
        IGRAPH_FINALLY_CLEAN(1);
    }

    return 0;
}

static igraph_bool_t igraph_i_subisomorphic_vf2(
        const igraph_vector_t *map12,
        const igraph_vector_t *map21,
        void *arg) {
    igraph_i_iso_cb_data_t *data = arg;
    igraph_bool_t *iso = data->arg;
    IGRAPH_UNUSED(map12); IGRAPH_UNUSED(map21);
    *iso = 1;
    return 0; /* stop */
}

/**
 * \function igraph_subisomorphic_vf2
 * Decide subgraph isomorphism using VF2
 *
 * Decides whether a subgraph of \p graph1 is isomorphic to \p
 * graph2. It uses \ref igraph_subisomorphic_function_vf2().
 * \param graph1 The first input graph, may be directed or
 *    undirected. This is supposed to be the larger graph.
 * \param graph2 The second input graph, it must have the same
 *    directedness as \p graph1. This is supposed to be the smaller
 *    graph.
 * \param vertex_color1 An optional color vector for the first graph. If
 *   color vectors are given for both graphs, then the subgraph isomorphism is
 *   calculated on the colored graphs; i.e. two vertices can match
 *   only if their color also matches. Supply a null pointer here if
 *   your graphs are not colored.
 * \param vertex_color2 An optional color vector for the second graph. See
 *   the previous argument for explanation.
 * \param edge_color1 An optional edge color vector for the first
 *   graph. The matching edges in the two graphs must have matching
 *   colors as well. Supply a null pointer here if your graphs are not
 *   edge-colored.
 * \param edge_color2 The edge color vector for the second graph.
 * \param iso Pointer to a boolean. The result of the decision problem
 *    is stored here.
 * \param map12 Pointer to a vector or \c NULL. If not \c NULL, then an
 *    isomorphic mapping from \p graph1 to \p graph2 is stored here.
 * \param map21 Pointer to a vector ot \c NULL. If not \c NULL, then
 *    an isomorphic mapping from \p graph2 to \p graph1 is stored
 *    here.
 * \param node_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two nodes are compatible.
 * \param edge_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two edges are compatible.
 * \param arg Extra argument to supply to functions \p node_compat_fn
 *   and \p edge_compat_fn.
 * \return Error code.
 *
 * Time complexity: exponential.
 */

int igraph_subisomorphic_vf2(const igraph_t *graph1, const igraph_t *graph2,
                             const igraph_vector_int_t *vertex_color1,
                             const igraph_vector_int_t *vertex_color2,
                             const igraph_vector_int_t *edge_color1,
                             const igraph_vector_int_t *edge_color2,
                             igraph_bool_t *iso, igraph_vector_t *map12,
                             igraph_vector_t *map21,
                             igraph_isocompat_t *node_compat_fn,
                             igraph_isocompat_t *edge_compat_fn,
                             void *arg) {

    igraph_i_iso_cb_data_t data = { node_compat_fn, edge_compat_fn, iso, arg };
    igraph_isocompat_t *ncb = node_compat_fn ? igraph_i_isocompat_node_cb : 0;
    igraph_isocompat_t *ecb = edge_compat_fn ? igraph_i_isocompat_edge_cb : 0;

    *iso = 0;
    IGRAPH_CHECK(igraph_subisomorphic_function_vf2(graph1, graph2,
                 vertex_color1, vertex_color2,
                 edge_color1, edge_color2,
                 map12, map21,
                 (igraph_isohandler_t *)
                 igraph_i_subisomorphic_vf2,
                 ncb, ecb, &data));
    if (! *iso) {
        if (map12) {
            igraph_vector_clear(map12);
        }
        if (map21) {
            igraph_vector_clear(map21);
        }
    }
    return 0;
}

static igraph_bool_t igraph_i_count_subisomorphisms_vf2(
        const igraph_vector_t *map12,
        const igraph_vector_t *map21,
        void *arg) {
    igraph_i_iso_cb_data_t *data = arg;
    igraph_integer_t *count = data->arg;
    IGRAPH_UNUSED(map12); IGRAPH_UNUSED(map21);
    *count += 1;
    return 1;         /* always continue */
}

/**
 * \function igraph_count_subisomorphisms_vf2
 * Number of subgraph isomorphisms using VF2
 *
 * Count the number of isomorphisms between subgraphs of \p graph1 and
 * \p graph2. This function uses \ref
 * igraph_subisomorphic_function_vf2().
 * \param graph1 The first input graph, may be directed or
 *    undirected. This is supposed to be the larger graph.
 * \param graph2 The second input graph, it must have the same
 *    directedness as \p graph1. This is supposed to be the smaller
 *    graph.
 * \param vertex_color1 An optional color vector for the first graph. If
 *   color vectors are given for both graphs, then the subgraph isomorphism is
 *   calculated on the colored graphs; i.e. two vertices can match
 *   only if their color also matches. Supply a null pointer here if
 *   your graphs are not colored.
 * \param vertex_color2 An optional color vector for the second graph. See
 *   the previous argument for explanation.
 * \param edge_color1 An optional edge color vector for the first
 *   graph. The matching edges in the two graphs must have matching
 *   colors as well. Supply a null pointer here if your graphs are not
 *   edge-colored.
 * \param edge_color2 The edge color vector for the second graph.
 * \param count Pointer to an integer. The number of subgraph
 *    isomorphisms is stored here.
 * \param node_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two nodes are compatible.
 * \param edge_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two edges are compatible.
 * \param arg Extra argument to supply to functions \p node_compat_fn and
 *   \p edge_compat_fn.
 * \return Error code.
 *
 * Time complexity: exponential.
 */

int igraph_count_subisomorphisms_vf2(const igraph_t *graph1, const igraph_t *graph2,
                                     const igraph_vector_int_t *vertex_color1,
                                     const igraph_vector_int_t *vertex_color2,
                                     const igraph_vector_int_t *edge_color1,
                                     const igraph_vector_int_t *edge_color2,
                                     igraph_integer_t *count,
                                     igraph_isocompat_t *node_compat_fn,
                                     igraph_isocompat_t *edge_compat_fn,
                                     void *arg) {

    igraph_i_iso_cb_data_t data = { node_compat_fn, edge_compat_fn,
                                    count, arg
                                  };
    igraph_isocompat_t *ncb = node_compat_fn ? igraph_i_isocompat_node_cb : 0;
    igraph_isocompat_t *ecb = edge_compat_fn ? igraph_i_isocompat_edge_cb : 0;
    *count = 0;
    IGRAPH_CHECK(igraph_subisomorphic_function_vf2(graph1, graph2,
                 vertex_color1, vertex_color2,
                 edge_color1, edge_color2,
                 0, 0,
                 (igraph_isohandler_t*)
                 igraph_i_count_subisomorphisms_vf2,
                 ncb, ecb, &data));
    return 0;
}

static void igraph_i_get_subisomorphisms_free(igraph_vector_ptr_t *data) {
    long int i, n = igraph_vector_ptr_size(data);
    for (i = 0; i < n; i++) {
        igraph_vector_t *vec = VECTOR(*data)[i];
        igraph_vector_destroy(vec);
        igraph_free(vec);
    }
}

static igraph_bool_t igraph_i_get_subisomorphisms_vf2(
        const igraph_vector_t *map12,
        const igraph_vector_t *map21,
        void *arg) {

    igraph_i_iso_cb_data_t *data = arg;
    igraph_vector_ptr_t *vector = data->arg;
    igraph_vector_t *newvector = igraph_Calloc(1, igraph_vector_t);
    IGRAPH_UNUSED(map12);
    if (!newvector) {
        igraph_error("Out of memory", __FILE__, __LINE__, IGRAPH_ENOMEM);
        return 0;           /* stop right here */
    }
    IGRAPH_FINALLY(igraph_free, newvector);
    IGRAPH_CHECK(igraph_vector_copy(newvector, map21));
    IGRAPH_FINALLY(igraph_vector_destroy, newvector);
    IGRAPH_CHECK(igraph_vector_ptr_push_back(vector, newvector));
    IGRAPH_FINALLY_CLEAN(2);

    return 1;         /* continue finding subisomorphisms */
}

/**
 * \function igraph_get_subisomorphisms_vf2
 * Return all subgraph isomorphic mappings
 *
 * This function collects all isomorphic mappings of \p graph2 to a
 * subgraph of \p graph1. It uses the \ref
 * igraph_subisomorphic_function_vf2() function.
 * \param graph1 The first input graph, may be directed or
 *    undirected. This is supposed to be the larger graph.
 * \param graph2 The second input graph, it must have the same
 *    directedness as \p graph1. This is supposed to be the smaller
 *    graph.
 * \param vertex_color1 An optional color vector for the first graph. If
 *   color vectors are given for both graphs, then the subgraph isomorphism is
 *   calculated on the colored graphs; i.e. two vertices can match
 *   only if their color also matches. Supply a null pointer here if
 *   your graphs are not colored.
 * \param vertex_color2 An optional color vector for the second graph. See
 *   the previous argument for explanation.
 * \param edge_color1 An optional edge color vector for the first
 *   graph. The matching edges in the two graphs must have matching
 *   colors as well. Supply a null pointer here if your graphs are not
 *   edge-colored.
 * \param edge_color2 The edge color vector for the second graph.
 * \param maps Pointer vector. On return it contains pointers to
 *   \ref igraph_vector_t objects, each vector is an
 *   isomorphic mapping of \p graph2 to a subgraph of \p graph1. Please note that
 *   you need to 1) Destroy the vectors via \ref
 *   igraph_vector_destroy(), 2) free them via
 *   \ref igraph_free() and then 3) call \ref
 *   igraph_vector_ptr_destroy() on the pointer vector to deallocate all
 *   memory when \p maps is no longer needed.
 * \param node_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two nodes are compatible.
 * \param edge_compat_fn A pointer to a function of type \ref
 *   igraph_isocompat_t. This function will be called by the algorithm to
 *   determine whether two edges are compatible.
 * \param arg Extra argument to supply to functions \p node_compat_fn
 *   and \p edge_compat_fn.
 * \return Error code.
 *
 * Time complexity: exponential.
 */

int igraph_get_subisomorphisms_vf2(const igraph_t *graph1,
                                   const igraph_t *graph2,
                                   const igraph_vector_int_t *vertex_color1,
                                   const igraph_vector_int_t *vertex_color2,
                                   const igraph_vector_int_t *edge_color1,
                                   const igraph_vector_int_t *edge_color2,
                                   igraph_vector_ptr_t *maps,
                                   igraph_isocompat_t *node_compat_fn,
                                   igraph_isocompat_t *edge_compat_fn,
                                   void *arg) {

    igraph_i_iso_cb_data_t data = { node_compat_fn, edge_compat_fn, maps, arg };
    igraph_isocompat_t *ncb = node_compat_fn ? igraph_i_isocompat_node_cb : 0;
    igraph_isocompat_t *ecb = edge_compat_fn ? igraph_i_isocompat_edge_cb : 0;

    igraph_vector_ptr_clear(maps);
    IGRAPH_FINALLY(igraph_i_get_subisomorphisms_free, maps);
    IGRAPH_CHECK(igraph_subisomorphic_function_vf2(graph1, graph2,
                 vertex_color1, vertex_color2,
                 edge_color1, edge_color2,
                 0, 0,
                 (igraph_isohandler_t*)
                 igraph_i_get_subisomorphisms_vf2,
                 ncb, ecb, &data));
    IGRAPH_FINALLY_CLEAN(1);
    return 0;
}

/**
 * \function igraph_permute_vertices
 * Permute the vertices
 *
 * This function creates a new graph from the input graph by permuting
 * its vertices according to the specified mapping. Call this function
 * with the output of \ref igraph_canonical_permutation() to create
 * the canonical form of a graph.
 * \param graph The input graph.
 * \param res Pointer to an uninitialized graph object. The new graph
 *    is created here.
 * \param permutation The permutation to apply. Vertex 0 is mapped to
 *    the first element of the vector, vertex 1 to the second,
 * etc. Note that it is not checked that the vector contains every
 *    element only once, and no range checking is performed either.
 * \return Error code.
 *
 * Time complexity: O(|V|+|E|), linear in terms of the number of
 * vertices and edges.
 */

int igraph_permute_vertices(const igraph_t *graph, igraph_t *res,
                            const igraph_vector_t *permutation) {

    long int no_of_nodes = igraph_vcount(graph);
    long int no_of_edges = igraph_ecount(graph);
    igraph_vector_t edges;
    long int i, p = 0;

    if (igraph_vector_size(permutation) != no_of_nodes) {
        IGRAPH_ERROR("Permute vertices: invalid permutation vector size", IGRAPH_EINVAL);
    }

    IGRAPH_VECTOR_INIT_FINALLY(&edges, no_of_edges * 2);

    for (i = 0; i < no_of_edges; i++) {
        VECTOR(edges)[p++] = VECTOR(*permutation)[ (long int) IGRAPH_FROM(graph, i) ];
        VECTOR(edges)[p++] = VECTOR(*permutation)[ (long int) IGRAPH_TO(graph, i) ];
    }

    IGRAPH_CHECK(igraph_create(res, &edges, (igraph_integer_t) no_of_nodes,
                               igraph_is_directed(graph)));

    /* Attributes */
    if (graph->attr) {
        igraph_vector_t index;
        igraph_vector_t vtypes;
        IGRAPH_I_ATTRIBUTE_DESTROY(res);
        IGRAPH_I_ATTRIBUTE_COPY(res, graph, /*graph=*/1, /*vertex=*/0, /*edge=*/1);
        IGRAPH_VECTOR_INIT_FINALLY(&vtypes, 0);
        IGRAPH_CHECK(igraph_i_attribute_get_info(graph, 0, 0, 0, &vtypes, 0, 0));
        if (igraph_vector_size(&vtypes) != 0) {
            IGRAPH_VECTOR_INIT_FINALLY(&index, no_of_nodes);
            for (i = 0; i < no_of_nodes; i++) {
                VECTOR(index)[ (long int) VECTOR(*permutation)[i] ] = i;
            }
            IGRAPH_CHECK(igraph_i_attribute_permute_vertices(graph, res, &index));
            igraph_vector_destroy(&index);
            IGRAPH_FINALLY_CLEAN(1);
        }
        igraph_vector_destroy(&vtypes);
        IGRAPH_FINALLY_CLEAN(1);
    }

    igraph_vector_destroy(&edges);
    IGRAPH_FINALLY_CLEAN(1);
    return 0;
}

/**
 * \section about_bliss
 *
 * <para>
 * BLISS is a successor of the famous NAUTY algorithm and
 * implementation. While using the same ideas in general, with better
 * heuristics and data structures BLISS outperforms NAUTY on most
 * graphs.
 * </para>
 *
 * <para>
 * BLISS was developed and implemented by Tommi Junttila and Petteri Kaski at
 * Helsinki University of Technology, Finland. For more information,
 * see the BLISS homepage at http://www.tcs.hut.fi/Software/bliss/ and the publication
 * Tommi Junttila, Petteri Kaski: "Engineering an Efficient Canonical Labeling
 * Tool for Large and Sparse Graphs" at https://doi.org/10.1137/1.9781611972870.13
 * </para>
 *
 * <para>
 * BLISS works with both directed graphs and undirected graphs. It supports graphs with
 * self-loops, but not graphs with multi-edges.
 * </para>
 *
 * <para>
 * BLISS version 0.73 is included in igraph.
 * </para>
 */

/**
 * \function igraph_isomorphic_bliss
 * Graph isomorphism via BLISS
 *
 * This function uses the BLISS graph isomorphism algorithm, a
 * successor of the famous NAUTY algorithm and implementation. BLISS
 * is open source and licensed according to the GNU GPL. See
 * http://www.tcs.hut.fi/Software/bliss/index.html for
 * details. Currently the 0.73 version of BLISS is included in igraph.
 *
 * </para><para>
 *
 * \param graph1 The first input graph. Multiple edges between the same nodes
 *   are not supported and will cause an incorrect result to be returned.
 * \param graph2 The second input graph. Multiple edges between the same nodes
 *   are not supported and will cause an incorrect result to be returned.
 * \param colors1 An optional vertex color vector for the first graph. Supply a
 *   null pointer if your graph is not colored.
 * \param colors2 An optional vertex color vector for the second graph. Supply a
 *   null pointer if your graph is not colored.
 * \param iso Pointer to a boolean, the result is stored here.
 * \param map12 A vector or \c NULL pointer. If not \c NULL then an
 *   isomorphic mapping from \p graph1 to \p graph2 is stored here.
 *   If the input graphs are not isomorphic then this vector is
 *   cleared, i.e. it will have length zero.
 * \param map21 Similar to \p map12, but for the mapping from \p
 *   graph2 to \p graph1.
 * \param sh Splitting heuristics to be used for the graphs. See
 *   \ref igraph_bliss_sh_t.
 * \param info1 If not \c NULL, information about the canonization of
 *    the first input graph is stored here. See \ref igraph_bliss_info_t
 *    for details. Note that if the two graphs have different number
 *    of vertices or edges, then this is not filled.
 * \param info2 Same as \p info1, but for the second graph.
 * \return Error code.
 *
 * Time complexity: exponential, but in practice it is quite fast.
 */

int igraph_isomorphic_bliss(const igraph_t *graph1, const igraph_t *graph2,
                            const igraph_vector_int_t *colors1, const igraph_vector_int_t *colors2,
                            igraph_bool_t *iso, igraph_vector_t *map12,
                            igraph_vector_t *map21, igraph_bliss_sh_t sh,
                            igraph_bliss_info_t *info1, igraph_bliss_info_t *info2) {

    long int no_of_nodes = igraph_vcount(graph1);
    long int no_of_edges = igraph_ecount(graph1);
    igraph_vector_t perm1, perm2;
    igraph_vector_t vmap12, *mymap12 = &vmap12;
    igraph_vector_t from, to, index;
    igraph_vector_t from2, to2, index2;
    igraph_bool_t directed;
    long int i, j;

    *iso = 0;
    if (info1) {
        info1->nof_nodes = info1->nof_leaf_nodes = info1->nof_bad_nodes =
                               info1->nof_canupdates = info1->max_level = info1->nof_generators = -1;
        info1->group_size = 0;
    }
    if (info2) {
        info2->nof_nodes = info2->nof_leaf_nodes = info2->nof_bad_nodes =
                               info2->nof_canupdates = info2->max_level = info2->nof_generators = -1;
        info2->group_size = 0;
    }

    directed = igraph_is_directed(graph1);
    if (igraph_is_directed(graph2) != directed) {
        IGRAPH_ERROR("Cannot compare directed and undirected graphs",
                     IGRAPH_EINVAL);
    }
    if ((colors1 == NULL || colors2 == NULL) && colors1 != colors2) {
        IGRAPH_WARNING("Only one of the graphs is vertex colored, colors will be ignored");
        colors1 = NULL; colors2 = NULL;
    }

    if (no_of_nodes != igraph_vcount(graph2) ||
        no_of_edges != igraph_ecount(graph2)) {
        if (map12) {
            igraph_vector_clear(map12);
        }
        if (map21) {
            igraph_vector_clear(map21);
        }
        return 0;
    }

    if (map12) {
        mymap12 = map12;
    } else {
        IGRAPH_VECTOR_INIT_FINALLY(mymap12, 0);
    }

    IGRAPH_VECTOR_INIT_FINALLY(&perm1, no_of_nodes);
    IGRAPH_VECTOR_INIT_FINALLY(&perm2, no_of_nodes);

    IGRAPH_CHECK(igraph_canonical_permutation(graph1, colors1, &perm1, sh, info1));
    IGRAPH_CHECK(igraph_canonical_permutation(graph2, colors2, &perm2, sh, info2));

    IGRAPH_CHECK(igraph_vector_resize(mymap12, no_of_nodes));

    /* The inverse of perm2 is produced in mymap12 */
    for (i = 0; i < no_of_nodes; i++) {
        VECTOR(*mymap12)[ (long int)VECTOR(perm2)[i] ] = i;
    }
    /* Now we produce perm2^{-1} o perm1 in perm2 */
    for (i = 0; i < no_of_nodes; i++) {
        VECTOR(perm2)[i] = VECTOR(*mymap12)[ (long int) VECTOR(perm1)[i] ];
    }
    /* Copy it to mymap12 */
    igraph_vector_update(mymap12, &perm2);

    igraph_vector_destroy(&perm1);
    igraph_vector_destroy(&perm2);
    IGRAPH_FINALLY_CLEAN(2);

    /* Check isomorphism, we apply the permutation in mymap12 to graph1
       and should get graph2 */

    IGRAPH_VECTOR_INIT_FINALLY(&from, no_of_edges);
    IGRAPH_VECTOR_INIT_FINALLY(&to, no_of_edges);
    IGRAPH_VECTOR_INIT_FINALLY(&index, no_of_edges);
    IGRAPH_VECTOR_INIT_FINALLY(&from2, no_of_edges * 2);
    IGRAPH_VECTOR_INIT_FINALLY(&to2, no_of_edges);
    IGRAPH_VECTOR_INIT_FINALLY(&index2, no_of_edges);

    for (i = 0; i < no_of_edges; i++) {
        VECTOR(from)[i] = VECTOR(*mymap12)[ (long int) IGRAPH_FROM(graph1, i) ];
        VECTOR(to)[i]   = VECTOR(*mymap12)[ (long int) IGRAPH_TO  (graph1, i) ];
        if (! directed && VECTOR(from)[i] < VECTOR(to)[i]) {
            igraph_real_t tmp = VECTOR(from)[i];
            VECTOR(from)[i] = VECTOR(to)[i];
            VECTOR(to)[i] = tmp;
        }
    }
    igraph_vector_order(&from, &to, &index, no_of_nodes);

    igraph_get_edgelist(graph2, &from2, /*bycol=*/ 1);
    for (i = 0, j = no_of_edges; i < no_of_edges; i++, j++) {
        VECTOR(to2)[i] = VECTOR(from2)[j];
        if (! directed && VECTOR(from2)[i] < VECTOR(to2)[i]) {
            igraph_real_t tmp = VECTOR(from2)[i];
            VECTOR(from2)[i] = VECTOR(to2)[i];
            VECTOR(to2)[i] = tmp;
        }
    }
    igraph_vector_resize(&from2, no_of_edges);
    igraph_vector_order(&from2, &to2, &index2, no_of_nodes);

    *iso = 1;
    for (i = 0; i < no_of_edges; i++) {
        long int i1 = (long int) VECTOR(index)[i];
        long int i2 = (long int) VECTOR(index2)[i];
        if (VECTOR(from)[i1] != VECTOR(from2)[i2] ||
            VECTOR(to)[i1] != VECTOR(to2)[i2]) {
            *iso = 0;
            break;
        }
    }

    /* If the graphs are coloured, we also need to check that applying the
       permutation mymap12 to colors1 gives colors2. */

    if (*iso && colors1 != NULL) {
        for (i = 0; i < no_of_nodes; i++) {
            if (VECTOR(*colors1)[i] != VECTOR(*colors2)[(long int) VECTOR(*mymap12)[i] ]) {
                *iso = 0;
                break;
            }
        }
    }

    igraph_vector_destroy(&index2);
    igraph_vector_destroy(&to2);
    igraph_vector_destroy(&from2);
    igraph_vector_destroy(&index);
    igraph_vector_destroy(&to);
    igraph_vector_destroy(&from);
    IGRAPH_FINALLY_CLEAN(6);

    if (*iso) {
        /* The inverse of mymap12 */
        if (map21) {
            IGRAPH_CHECK(igraph_vector_resize(map21, no_of_nodes));
            for (i = 0; i < no_of_nodes; i++) {
                VECTOR(*map21)[ (long int) VECTOR(*mymap12)[i] ] = i;
            }
        }
    } else {
        if (map12) {
            igraph_vector_clear(map12);
        }
        if (map21) {
            igraph_vector_clear(map21);
        }
    }

    if (!map12) {
        igraph_vector_destroy(mymap12);
        IGRAPH_FINALLY_CLEAN(1);
    }

    return 0;
}


/**
 * \function igraph_simplify_and_colorize
 * \brief Simplify the graph and compute self-loop and edge multiplicities.
 *
 * </para><para>
 * This function creates a vertex and edge colored simple graph from the input
 * graph. The vertex colors are computed as the number of incident self-loops
 * to each vertex in the input graph. The edge colors are computed as the number of
 * parallel edges in the input graph that were merged to create each edge
 * in the simple graph.
 *
 * </para><para>
 * The resulting colored simple graph is suitable for use by isomorphism checking
 * algorithms such as VF2, which only support simple graphs, but can consider
 * vertex and edge colors.
 *
 * \param graph The graph object, typically having self-loops or multi-edges.
 * \param res An uninitialized graph object. The result will be stored here
 * \param vertex_color Computed vertex colors corresponding to self-loop multiplicities.
 * \param edge_color Computed edge colors corresponding to edge multiplicities
 * \return Error code.
 *
 * \sa \ref igraph_simplify(), \ref igraph_isomorphic_vf2(), \ref igraph_subisomorphic_vf2()
 *
 */
int igraph_simplify_and_colorize(
    const igraph_t *graph, igraph_t *res,
    igraph_vector_int_t *vertex_color, igraph_vector_int_t *edge_color) {
    igraph_es_t es;
    igraph_eit_t eit;
    igraph_vector_t edges;
    long int no_of_nodes = igraph_vcount(graph);
    long int no_of_edges = igraph_ecount(graph);
    long int pto = -1, pfrom = -1;
    long int i;

    IGRAPH_CHECK(igraph_es_all(&es, IGRAPH_EDGEORDER_FROM));
    IGRAPH_FINALLY(igraph_es_destroy, &es);
    IGRAPH_CHECK(igraph_eit_create(graph, es, &eit));
    IGRAPH_FINALLY(igraph_eit_destroy, &eit);

    IGRAPH_VECTOR_INIT_FINALLY(&edges, 0);
    IGRAPH_CHECK(igraph_vector_reserve(&edges, no_of_edges * 2));

    IGRAPH_CHECK(igraph_vector_int_resize(vertex_color, no_of_nodes));
    igraph_vector_int_null(vertex_color);

    IGRAPH_CHECK(igraph_vector_int_resize(edge_color, no_of_edges));
    igraph_vector_int_null(edge_color);

    i = -1;
    for (; !IGRAPH_EIT_END(eit); IGRAPH_EIT_NEXT(eit)) {
        long int edge = IGRAPH_EIT_GET(eit);
        long int from = IGRAPH_FROM(graph, edge);
        long int to   = IGRAPH_TO(graph, edge);

        if (to == from) {
            VECTOR(*vertex_color)[to]++;
            continue;
        }

        if (to == pto && from == pfrom) {
            VECTOR(*edge_color)[i]++;
        } else {
            igraph_vector_push_back(&edges, from);
            igraph_vector_push_back(&edges, to);
            i++;
            VECTOR(*edge_color)[i] = 1;
        }

        pfrom = from; pto = to;
    }

    igraph_vector_int_resize(edge_color, i + 1);

    igraph_eit_destroy(&eit);
    igraph_es_destroy(&es);
    IGRAPH_FINALLY_CLEAN(2);

    IGRAPH_CHECK(igraph_create(res, &edges, no_of_nodes, igraph_is_directed(graph)));

    igraph_vector_destroy(&edges);
    IGRAPH_FINALLY_CLEAN(1);

    return IGRAPH_SUCCESS;
}
